damage: Remove the 'damage window' resource type.

damage: Remove the 'damage window' resource type.

Note that the existing code never actually creates a resource of this
type, so it can't possibly do anything.  This is clearly meant to track
window destruction and clean up any associated Damages, but that's
already handled by miext/damage's DestroyWindow wrapper.

Previous discussion:
http://lists.freedesktop.org/archives/xorg-devel/2011-March/020847.html

Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Adam Jackson <ajax@redhat.com>