ports/76257: nvidia_driver breaks xorg-clients build

[Mikhail Teterin]

> It was already changed in my patch. Do you have any better suggestions?

Not really...

> As I mentioned in an earlier mail, the GLX headers from Xorg don't seem
> to define the ARB function any more.

6.8.1 still has it. Not sure about 6.8.2. In that case, the following little 
hunk:

	+#ifndef GLX_VERSION_1_4
	+#	define glXGetProcAddress	glXGetProcAddressARB
	+#endif

seems less intrusive :-) The utility will still not *work* when compiled 
against GLX-1.3 headers, but it will *compile*.

To allow for -lGL to be interchangible post-build, however, it may be required 
to make a dlopen/dlsym search for the glXGetProcAddress symbol at run-time.

Would you like a patch? It will, unavoidably, system-specific, but should work 
on most (all?) systems supported by Xorg. You will also be able to remove 
this hack in a few years, when all available GLX implementations are 
upgraded. Yours,

	-mi