Codechange: [OpenGL] Load all OpenGL functions dynamically. #8730
Motivation / Problem
Some Linux OpenGL drivers don't use the global system dispatch table.
Link all OpenGL functions dynamically to make sure we use the right one.
OpenGL headers are not uniform among systems, which might cause compile problems on more obscure systems.
Checklist for review
Some things are not automated, and forgotten often. This list is a reminder for the reviewers.
With this PR, I can remove
I can PR that after this PR, if you like, but maybe the