Revert "Update to latest xdg-shell protocol"

This reverts commit eed03d38b022ef018aed8ceb07ea78ce19db0774.

This was pushed by accident.
backend-x11: Don't use clutter_stage_get_default

It turns out Clutter doesn't actually set the stage as the default
when creating a new one, so this creates a new stage that then dies.