gdk_display_get_event: don't unqueue events from the windowing system when paused

Unqueuing events from the windowing system when paused could result
in weird reordering if event filters resulted in application-visible
behavior. Since we now resume events when the frame clock is frozen,
we now no longer count on low-level event handling running while
event handling is paused.

https://bugzilla.gnome.org/show_bug.cgi?id=685460