GLX Khronos sync
Syncs glxext.h with Khronos with accompanying minor fixups, and then fixes a buglet in __glXGetDrawableAttribute pointed out by one of the fixups.
Due to an influx of spam, we have had to impose restrictions on new accounts. Please see this wiki page for instructions on how to get full permissions. Sorry for the inconvenience.
Syncs glxext.h with Khronos with accompanying minor fixups, and then fixes a buglet in __glXGetDrawableAttribute pointed out by one of the fixups.