Mac: Modify Qt::SizeAllCursor to look like arrows

On Mac, Qt::SizeAllCursor showed a spreadsheet cell selection cursor.
It has been changed to look like it looks in the Qt Documentation.

Task-number: QTBUG-27577
Change-Id: I2d50ab0d813137366b56cb30b8784ecf70392d4e
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>