SeExpr library and demos are vulnerable to the current C locale

[amyspark]

Hey,

I've tried compiling SeExpr's demos with Qt 5.12.7 on Manjaro and macOS Mojave (the latter through Homebrew).

In both cases, the ccolor widget in the Image Synthesis Editor initializes to a default yellow value and forcibly overrides the value set in the script. This doesn't happen in Windows 10 x64 (with the same Qt version).

The reason is that, in the Bison parser and the imageEditor demo all floating point parameters are parsed using atof(). Under Qt-based apps, the LANG and LC_ALL environment variables govern floating-point number format. I'm using es_ES.UTF8, which re-uses , as the decimal point separator.

[davvid]

We'd be happy to take fixes in this area. It'd be good to make the code not dependent on the locale.