Removed unused post-processing class
Removed custom texture class, FHardwareTexture is used instead
Fixed offscreen rendering to texture using FBO
Removed template classes, the last remnants of GL auxilium
GL_EXT_framebuffer_object is used instead of corresponding ARB extension

This allows to run on OS X 10.5 and potentially 10.4
Merge branch 'gz_osx' of https://github.com/alexey-lysiuk/gzdoom into osx