I never liked it, but with C2x coming out, it's best to handle bools
properly. I haven't gone through all the uses of int as bool (I'll leave
that for fixing when I encounter them), but this gets QF working with
both c2x (really, gnu2x because of raw strings).
Add GLSL directory to QF and use it for all gsls based code (instead of
GL). defines.h, types.h and funcs.h are derived from gl2.h from khronos.
Text drawing now uses triangles instead of quads.
