Change mouse and wheel QPA events to use QPointF.

Change mouse and wheel QPA events to use QPointF.

At least QMouseEvent already uses QPointF so there is no reason to
restrict handleMouseEvent to integer positions.

Change-Id: I9c72d2e0e99518b40a1898aec9ad2b3421a3e9e2
Reviewed-on: http://codereview.qt.nokia.com/2739
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Samuel Rødal <samuel.rodal@nokia.com>