As it turns out, 4 of our current tests are not valgrind clean,
(use after free errors or so), so this will be helpful for
investigating and fixing those.
These were only ever intended to exist in the original, standalone
implementation of glcpp, (with the idea of dropping them as soon as
the code moved into mesa). The current build system wasn't compiling
this C file, but the presence of the header files could cause problems
if the two copies diverge in the future.
We head those problems off by deleting al of these redundant files.
Currently only GL_ARB_draw_buffers and GL_ARB_texture_rectangle are
defined because those extensions are always enabled. This make
tex_rect-03.frag pass.
