Update Khronos-supplied headers

Taken from commit 676834dd529d620ee25090e738d2607dfde003d8
of https://github.com/KhronosGroup/OpenGL-Registry.git

v2:
- keep the BUILDING_MESA bits (Matt)

Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
16 files changed