[reg] QGraphicsTextItem's text is shifted one pixel down

The baseline of the text in QGrapicsTextItem has moved one pixel down in 4.6 compared to 4.5.3.
It seems something changed in the way the documentSize of the text is calculated.

This changed between 4.5.3 and 4.6.0

This can be reproduced using the diagramscene example in examples/graphicsview/
A given text line will in 4.6 be shifted one pixel down and the boundingRect is 1 px smaller in height.

This is a problem on both Windows and Mac, but more visible on Mac.