Make Std.parseFloat() locale independant?

Currently, ``Std.parseFloat()`` in HXCPP relies on ``strtod()``:

https://github.com/HaxeFoundation/hxcpp/blob/31500dc4bdc1b78729f6865c5a419a4ec5e2acaf/src/hx/StdLibs.cpp#L669-L683

The problem with ``strtod()`` is that its parsing of floats is dependant on the current locale. I learnt that the hard way when updating SDL to version 2.0.9, which is changing the locale in one of its dependencies (hidapi), making, for instance, ``Std.parseFloat('3.5')`` return ``3`` instead of ``3.5`` because the new locale was accepting ``,`` instead of ``.``, breaking my whole project code which relies on Std.parseFloat to parse large JSON file (for Spine animations).

My current workaround is to ensure the locale for parsing numbers is:

```
setlocale(LC_NUMERIC, "C");
```

But ideally, it may be nice to ensure ``Std.parseFloat()`` doesn't depend at all on the locale. What are your thoughs on this?