QtBase: combine adjacent qDebug()/qCritical() lines

For qDebug() and qWarning(), this is just an optimization.
For qCritical(), which can be fatal, the old code was just wrong.

Change-Id: I6d8ab1d7531d766cd41b49569dc0fd4420ecab8b
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>