mesa-headers: include gl.h and glx.h
mesa-headers: include gl.h and glx.h

Mesa still have a lot of custom code in their glx.h that differs from
Khronos and cairo depends on it.

triton/triton,triton/triton,triton/triton,triton/triton,triton/triton,triton/triton,triton/triton,triton/triton