There is now a meta_display_handle_event alongside the
meta_display_handle_xevent function which handles events in terms of
Clutter events instead of X events. A Clutter event filter is
registered so that all Clutter events will pass through this function.
The pointer event handling code from the X event version has been moved
into this new function and has been modified to use the details from
the Clutter event instead of the X event. This is a step towards
moving all of the event handling code over to use Clutter events.

Based-heavily-on-a-patch-by: Neil Roberts <neil@linux.intel.com>