Loading a TTF font generates many warnings to STDERR (v2.3.1 -- AWS Linux)

Using AWS Linux and node-canvas v2.3.1, when loading a simple TTF font, a bunch of warnings are printed to STDERR. Example:

```
Fontconfig warning: "/etc/fonts/conf.d/30-metric-aliases.conf", line 84: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/30-metric-aliases.conf", line 84: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/30-metric-aliases.conf", line 93: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/30-metric-aliases.conf", line 93: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/30-metric-aliases.conf", line 102: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/30-metric-aliases.conf", line 102: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 33: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 33: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 33: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 33: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 33: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 33: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 33: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 33: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 33: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 33: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 33: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 33: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 33: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 33: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 33: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 33: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 33: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 33: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 59: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 59: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 59: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 59: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 59: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 59: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 59: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 59: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 59: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 59: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 59: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 59: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 59: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 59: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 59: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 59: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 59: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 59: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 59: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 68: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 68: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 79: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 79: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 79: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 88: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 23: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 23: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 23: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 23: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 23: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 23: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 23: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 23: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 39: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 39: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 39: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 39: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 39: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 39: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 39: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 39: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 39: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 56: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 56: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 56: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 56: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 56: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 56: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 56: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 56: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 56: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 56: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 66: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 66: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 66: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 75: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 75: Having multiple in isn't supported and may not work as expected
Fontconfig warning: "/etc/fonts/fonts.conf", line 82: unknown element "blank"

Tests performed on Node.js v10.9.0, node-canvas v2.3.1 (Linux linux x64 4.14.62-65.117.amzn1.x86_64, 1957 MB RAM)
```

I understand these warnings may be legitimate (however this is a standard AWS Linux install), and my font config files may be malformed, but having these warnings emitted to STDERR every time I load a font is very noisy. Would it be possible to silence these, and/or emit them internally instead using an EventEmitter?

## Steps to Reproduce

```js
// node-canvas v2.x font load test
const { registerFont } = require('canvas');

registerFont( 'open-sans-regular.ttf', { family: "OpenSans" } );

const os = require('os');
console.log(
"Tests performed on Node.js " + process.version +
", node-canvas v" + require('canvas/package').version +
" (" + os.type() + " " + os.platform() + " " + os.arch() + " " +
os.release() + ", " + Math.floor( os.totalmem() / 1024 / 1024 ) + " MB RAM)"
);
```

## Related Files

Here is the font I am using (ISC license, okay to download): https://pixlcore.com/bugs/open-sans-regular.ttf

Here are my font config files from my AWS Linux instance, if it helps: https://pixlcore.com/bugs/etc-fonts.tar.gz

Those font config files were installed from this RPM: `fontconfig-2.8.0-5.8.amzn1.x86_64`

## Your Environment

Using AWS Linux and Node v10.9.0, node-canvas v2.3.1 (Linux linux x64 4.14.62-65.117.amzn1.x86_64, 1957 MB RAM)