Forcing painters renderer breaks images

I pulled the latest version (26eb699) of export_fig yesterday, so this should be directly reproducible.

This issue replicates #107 (superscripts in figure axes), but also goes further than this as the output from the `-opengl` vs `-painters` renderer option yields very different (and incorrect) output. This can be most easily described with examples.

So I generate a figure which looks fine on the screen, and using `-opengl` or `-painters` I get the following, for completeness the command is (with either renderer specified):
```
export_fig([out_dir,datestr(now,'yymmdd'),'_Fig',fignum],'-eps','-opengl')
```
So the **OPENGL** output looks like
And the **PAINTERS** output looks broken, with the fill seeming to be mixed across layers, like

A similar issue also occurs with another figure, so

**OPENGL**
**PAINTERS** with text missing along with lines that should be bolded not in the Pacific and Indian oceans

Is this an export_fig issue, or matlab?

For completeness:
```
MATLAB Version: 9.5.0.944444 (R2018b)
Operating System: Linux 2.6.32-754.3.5.el6.x86_64 #1 SMP Thu Aug 9 11:56:22 EDT 2018 x86_64
Java Version: Java 1.8.0_152-b16 with Oracle Corporation Java HotSpot(TM) 64-Bit Server VM mixed mode
Export_fig Version: current master (26eb699)
```