mesa: enable ARB_texture_buffer_* extensions in the Compatibility profile

mesa: enable ARB_texture_buffer_* extensions in the Compatibility profile

We already have piglit tests testing alpha, luminance, and intensity
formats. They were skipped by piglit until now.

Additionally, I'm enabling one ARB_texture_buffer_range piglit test to run
with the compat profile.

i965 behavior is unchanged except that it doesn't expose TBOs in the Compat
profile. Not sure how that affects the GL version override.

Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
Reviewed-by: Eric Anholt <eric@anholt.net>