Finish removing Qt3 support

Finish removing Qt3 support

Remove the (-no)-qt3support options from configure, and remove the last
remaining references to Qt3Support, QT3_SUPPORT, and
QEvent::ChildInserted.

The compatibilityChildInsertEvents() tests in tst_QObject and
tst_QWidget have been renamed to childEvents(), which is a more
appropriate name.

Change-Id: Id0b45e9b177efcc8dceee8c9ed8afafedeeace2f
Reviewed-by: Kai Koehne <kai.koehne@nokia.com>
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>
Reviewed-by: David Faure <faure@kde.org>
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>