ports/76257: nvidia_driver breaks xorg-clients build

[Mikhail Teterin]

> The attached patch (undo my other patch first) implements something like
> this without actually loading libGL dynamically. It uses
> dlopen(NULL, ...) to get a handle for the main program (including
> libGL).

Yes, this is what I had in mind.

> I hope this is portable. Does this work for you? 

I've seen `configure' scripts checking "whether dynamically linked program can 
dlopen itself". It can on Linux and FreeBSD...

> Note that the patch also changes the Imakefile. In xc/programs/xdriinfo
> run this to update the Makefile:
>
>         make Makefile
>         make depend
>
> Then recompile xdriinfo as usual.

Thanks! I'll try it, unless someone beats me to it. One thing, however (for 
now) -- when reporting failures of dlopen/dlsym, why not use dlerror() 
function to provide actual error message? Yours,

	-mi