Add helper for creating full-screen glX windows.

Signed-off-by: Jamey Sharp <jamey@minilop.net>
Signed-off-by: Theo Hill <Theo0x48@gmail.com>
fixup! glx-oml-sync-control: Added repeat-swapbuffer test
fixup! glx_oml_sync_control: Implemented timing test
Allow OML_sync_control tests to run fullscreen.

None of the current tests use this, but we introduce some fullscreen
tests in the next commit.

Signed-off-by: Jamey Sharp <jamey@minilop.net>
Signed-off-by: Theo Hill <Theo0x48@gmail.com>
fixup! glx-oml-sync-control: Added repeat-swapbuffer test