X11: Drop stoneold vsync methods

After debugging with @FernetMenta @grigorig and @ckoenig we found out, that Mesa still implements those old Vsync Methods. They don't seem to work as well as they did 10 years ago.

This fixes by accident the SlideShow, which did not show any image with intel display drivers an vertical blank sync = always enabled. It also chose this method. Furthermore it it improves number of skips we got while testing vdpau with uvd radeons.