server/multihead: xinerama button press test
server/multihead: xinerama button press test

If we have two windows on the left and right edge of the screen, ensure
that each gets the button events as expected.

Signed-off-by: Peter Hutterer <b9c50af7afa7642f6f854434cda9ffe54ece8b85@who-t.net>

freedesktop-unofficial-mirror/xorg__test__xorg-integration-tests,freedesktop-unofficial-mirror/xorg__test__xorg-integration-tests,freedesktop-unofficial-mirror/xorg__test__xorg-integration-tests