* Fixes for multi-DISPLAY and fullscreen support:
we now accept setting target==source if not initially set equal;
we correctly connect to source's DAMAGE events if source server isn't
the default GDK_DISPLAY;
we tear down the zoom regions in the magnifier when changing source as
well as target;
we correctly reparent the magnifier's zoom regions _after_ redefining
the magnifier's gtk-window;
better lifecycle management of the zoom regions themselves, so that
idle handlers and timeouts are removed when the regions are disposed.
