QQuickWindow: Add some more stuff under DBG_TOUCH.

This is useful for understanding when touch is actually delivered, and what it
goes to, which is useful for figuring out when something is incorrectly
filtering mouse events in the scene (for instance).

Change-Id: I9323629a42457b2b71e22ad489d8f1dc2d7b6fc5
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>