Move rarely used QObjectPrivate data to extraData

Move rarely used QObjectPrivate data to extraData

Move runningTimers, eventFilters and objectName data members to
ExtraData.  Saves 12 bytes per QObject for 95% of use cases
(QObjectPrivate goes from 76B -> 64B).

Change-Id: I5648c89f65a7be3ea51bd703ee8a9dcff6222c3c
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Roberto Raggi <roberto.raggi@nokia.com>
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>