sys/glsink/: A careful read of the documentation reveals that I can't use renderbuffe...

sys/glsink/: A careful read of the documentation reveals that I can't use renderbuffers as textures.  Duh.  Checkpoin...

Original commit message from CVS:
* sys/glsink/glextensions.c:
* sys/glsink/glextensions.h:
* sys/glsink/glvideo.c:
* sys/glsink/glvideo.h:
* sys/glsink/gstglbuffer.c:
* sys/glsink/gstgldownload.c:
* sys/glsink/gstglupload.c:
A careful read of the documentation reveals that I can't use
renderbuffers as textures.  Duh.  Checkpoint because I'm about
to rewrite a bunch of code.