protocol: specify behavior of get_pointer when capabilities change
protocol: specify behavior of get_pointer when capabilities change

Also applies to touch/keyboard

Signed-off-by: Peter Hutterer <b9c50af7afa7642f6f854434cda9ffe54ece8b85@who-t.net>
Reviewed-by: Daniel Stone <62e7e355d5d8400fa8384448796af0bf6be4ffae@collabora.com>
Reviewed-by: Derek Foreman <2f97e0f0bc172406aab8ccd42dab54c95bab8759@osg.samsung.com>
Reviewed-by: Jonas Ådahl <67dcd8a17e758192e0cbb577ce1d62cc7da6cf49@gmail.com>

mchalupa/wayland,mchalupa/wayland,sir-murray/wayland,sir-murray/wayland,sir-murray/wayland,mchalupa/wayland