Changes

components/x11/mesa: Link additional GL headers

These GL headers are currently missing from /usr/include/GL,
yet are expected by e.g. xorg-server during build.

Currently the headers stored /usr/include/GL are symlinks created
at runtime via ogl-select. This has been the case since ye olde days.

I don't particularly want to add further headers to ogl-select,
especially when the current supported method of doing this is
via libglvnd which actually supports multiple libgl implementations
on a single system.

Once mesa is in a better working state, I will proceed with enabling
libglvnd and we can retire ogl-select, and remove the links created
in this package.
 (commit: 2fab457)