Ensure the itemTransform in QInputPanel is always up to date

Hook into the render loop and update the itemTransform in
the QInputPanel before we repaint.

Change-Id: If9122ba0fbe31cff3bfcc3edc48f684cc9b16984
Reviewed-on: http://codereview.qt-project.org/4405


Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Vesa Rantanen <vesa.rantanen@nokia.com>
Reviewed-by: Gunnar Sletta <gunnar.sletta@nokia.com>