compositor-x11: Move the x11 window close to an idle handler

compositor-x11: Move the x11 window close to an idle handler

The input loop is actually dispatched in the middle of the frame repaint.
When the X11 event results in closing the compositor, this can cause the
current output to be destroyed just prior to trying to process animations
on it.

We fix this by handling the window close event in an idle callback.

NOTE: this requires a patch for wayland that moves the idle handler
dispatch to after epoll_wait in the event loop processing.

Closes bug: https://bugs.freedesktop.org/show_bug.cgi?id=81314

Signed-off-by: Derek Foreman <derekf@osg.samsung.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>