[Piglit] [PATCH 0/2 v2] GL_ARB_texture_compression query tests

[Ian Romanick]

The only change from the previous version is in patch 1/2.  I set the correct
base formats for GL_COMRPESSED_RED and GL_COMPRESSED_RG.  GL_RGB was
previously used for both because I had been looking at the
GL_ARB_texture_compression_rg spec.  That spec contains incorrect values that
contradict the OpenGL 3.x specs.  Using GL_RED and GL_RG matches the 3.x
specs.  I also added some comments.