compositor: Fix weston_subsurface_is_synchronized() return value.

Commit 280e7dd918f1717c7d677676384a9cd991097741 introduced a bug in the
return value of weston_subsurface_is_synchronized().

Signed-off-by: Carlos Olmedo Escobar <carlos.olmedo.e@gmail.com>
Reviewed-by: Derek Foreman <derekf@osg.samsung.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
compositor: Refactor weston_output_mode_switch()

This breaks weston_output_mode_switch() into 3 functions:
weston_output_mode_set_native()
weston_output_mode_switch_to_temporary()
weston_output_mode_switch_to_native()

Differences from previous behaviour:
SET_NATIVE didn't set current_scale (now it does)
SET_TEMPORARY could set mode and scale independently - now it can't.

Signed-off-by: Derek Foreman <derekf@osg.samsung.com>
Pekka Paalanen <pekka.paalanen@collabora.co.uk>
input: allow to destroy bindings in their handler

use wl_list_for_each_safe to iterate on the bindings list when
firing them, this way a binding can safely be destroyed in its
function handler.

Acked-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>