Fixed qqmlapplicationengine autotest build for QT_NO_PROCESS

Change-Id: Ie5993fac36a29a7d7edcadf5030dc2b5bf95b506
Reviewed-by: Andrew Knight <andrew.knight@digia.com>
QQuickWidget: handle resize to empty size

Resizing to an empty size needs to be handled as if the widget was
hidden. Restoring to a non-empty size is like a show, except that we
are rendering synchronously.

Task-number: QTBUG-37046
Change-Id: I572e4763c4a28bfe7347868e109acca5b357db50
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>