add QCoreApplication to bootstrap lib

this required making it compile with QT_NO_QOBJECT. of course this
disables anything related to threading and event processing.

needed for bootstrapping qmldevtools (qmlmin, lupdate)

Change-Id: I6f8bd3996ac7b6eee49a5b8a55143d358abe35ee
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>