QGraphicsLayoutItem::getContentsMargins violates Qt coding style

Came across this today: http://doc.qt.nokia.com/4.7/qgraphicslayoutitem.html#getContentsMargins

That's just poor API. Reasons:

• A getter function that returns void,
• A getter function in Qt with a get prefix,
• Four out params.

Proposed fix: Have a ContentsMargins struct that can be used as a return value. Will get rid of the out params. And drop the get prefix.