Add support for device-to-screen mapping

xinput map-to-crtc "device name" "VGA0" will map to the CRTC "VGA0" by
manipulating the transformation matrix accordingly. And because the NVIDIA
binary driver still exists, Xinerama is supported to. Maybe in another 5
years, they'll catch up.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Simon Thum <simon.thum@gmx.de>