Allow QtDeclarative and QtQml to co-exist at run-time

This patch changes QDeclarativeData to share the very first bit with QtQml's
QQmlData, to indicate ownership by either run-time. We need to check the bit in
the only QObject callback we use (destroyed), the other callback was unused and
removed.

Task-number: QTBUG-35006

Change-Id: Ife4b515648cba42b91612736ccd9375f1f46808a
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>