removed problem with OpenGL extensions under X11

[Lionel Ulmer]

> I added this check the day I found out that any Mesa-based GL library
> returns a non-NULL function pointer from glXGetPointerAddress whatever the
> status of the extension ... which leads to crashes if one actually calls
> this function without checking first for the presence of the extension.

Just answering myself to say that the same 'issue' is also present in the
D3D code and would need patching too :-)

          Lionel

-- 
		 Lionel Ulmer - http://www.bbrox.org/