GLX 1.3 / 1.4 support

[Felix Bellaby]

I might be missing something here, but I would have thought that a
functional implementation of GLX 1.3 / 1.4 would be remarkably easy to
add to the server. 

The SGI inherited code already does GLX 1.2 and all the fbconfig
requests.

Implementing CreateWindow need do little more than return the Window
argument as its result.

Implementing CreatePbuffer could simply return a GLXPixmap created with
the same arguments. This implementation of Pbuffers would mean that the
Pbuffer events would never need to be raised.

The other requests are already supported or trivial to implement.

If this is the case then it would make sense to code it. The current
situation with GL 1.2 and no GLX 1.3 is a violation of the GLX specs and
makes porting code to Xorg unnecessarily difficult. Failing to implement
GLX 1.3 in the Xorg server simply perpetuates the use of the obsolete
Visual based approach, which was superceeded for good reasons.

Adding support for GPU located Pbuffers would obviously be an entirely
different kettle of fish, but that could be a problem for another day.

Felix