wayland-server: log an error for events with wrong client objects

Check that all the objects in an event belong to the same client as
the resource posting it.  This prevents a compositor from accidentally
mixing client objects and posting an event that causes a client to
abort with a cryptic message.

Instead the client will now be disconnected as it is when the compositor
tries to send a null for a non-nullable object, and a log message
will be printed by the compositor.

Reviewed-by: Yong Bakos <ybakos@humanoriented.com>
Reviewed-by: Bryce Harrington <bryce@osg.samsung.com>
Signed-off-by: Derek Foreman <derekf@osg.samsung.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>