Added doom3 dxtc compression support (IL_RXGB)
Added doom3 dxtc compression support (IL_RXGB)


Agadoul/DevIL,bcampbell/DevIL,Agadoul/DevIL,DentonW/DevIL,bcampbell/DevIL,bcampbell/DevIL,Agadoul/DevIL,Agadoul/DevIL,DentonW/DevIL,DentonW/DevIL,DentonW/DevIL,DentonW/DevIL,DentonW/DevIL,bcampbell/DevIL,bcampbell/DevIL,Agadoul/DevIL,bcampbell/DevIL,Agadoul/DevIL