[Piglit] [PATCH] Make piglitutil library API-independent

[Chad Versace]

Blaz,

Thanks for splitting the earlier patch into this series of 5. As a result, the changes were much easier to review.
Everything looks good to me and is
  Reviewed-by: Chad Versace <chad.versace at linux.intel.com>
When you feel that the review process is complete and are ready to commit this, submit a pull request.

Since Piglit will soon have OpenCL tests, it is probably a good idea for us to begin renaming the GL-specific utility
symbols so that they are prefixed with `piglit_gl`. However, there is no rush there.

By the way, I briefly looked at your patch "cl: Add OpenCL support". I am not familiar with OpenCL, but CMake
modifications and the general direction of piglit-util-cl.c look good. I look forward to when the OpenCL tests begin
arriving.

-Chad