Fixing https://github.com/KhronosGroup/OpenGL-Registry/pull/149 enabled
including desktop OpenGL headers without conflicts, so we no longer
have to define enums for ARB extensions ourselves.

Change-Id: Ifa05112f1e1d21bb8a22b83519babbbb3e4d6462
Reviewed-on: https://swiftshader-review.googlesource.com/17909Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>