Blender Git Loki

OpenGL: use extension form of FBOs

FBOs are a GL 3.0 feature but enjoy nearly universal support via
extensions.

The newer ARB extension brings these features to GL 2.1 without needing
an ARB suffix.

The older EXT extensions *do* use a suffix. Since we don?t know which
is used until runtime, I added the suffix to all functions & enums.

Also updated the check to look for the FBO feature set instead of the
specific EXT extension.