Remove QGL pointers

This is a manual merge of Hecatomb Q2 ref b8952d5. Manual since git
couldn't do an automerge for some reasons... Notable changes are:
- QGL function pointers are removed, libGL is linked directly
- The OpenGL log framework is removed. It was disfunctional
- The gl_driver cvar is finaly gone
This change is currently untested on Windows and OS. There should
be no problems but a better Makefile integration of libGL is needed.
Only cleanup the GL context if OpenGL was initialized
Move refresher to client/refresh

This is the more appropriate place now that the refresher is merged into
the client
Alter Makefile and header pathes following the refresh move

With this change the "refresh" make target doesn't any longer exists.
It was merged into the "client" target. One will need a "make clean"
before building yQ2 after this change.