[em++]: Removed unnecessary warning about the PYTHON variable ;
[library_glut.js]: Handle DELETE & BACKSPACE correctly ;
[thirdparty/lzma.js]: Fixed doit.sh so that it compiles on Windows using MingW's GCC & Bash ;
Merge pull request #1761 from prenaux/develop

GLUT support for DELETE & BACKSPACE keys ; Fixed lzma.js doit.sh so that it works on Windows ; Removed unnecessary warning in em++ ;