Update to 2.1.0

Some hilights from release notes:

• adds support for OpenGL 4.6
• adds support for OSMesa and EGL
• Removes support for MX and removes related libraries

Use upstream install target instead of our own do-install:
Fix the pkgconfig script to actually tell something at least closer to the
truth.
Add missing GL dependencies.
Library version bump.

PR: 223370
Submitted by: zeising
exp-run by: antoine
Approved by: antoine