A little cleanup on the cleanup, just for consistency.
Fix for recent GLX error bug

Lee Salzman

I messed up in the patch I sent you regarding gobbling up the GLX error codes signaled when trying to create a context. After reading the spec I realized those error codes are relative to a base error that needs to be queried when setting up the GLX extension...

So I have made a patch that fixes it for a user I had who was still getting the bug with my old patch.

Without this patch my previous one won't work, so it is recommended to merge this...