Install event filter on Aurorae Decoration to handle WheelEvents

Unfortunately QtQuick 1 does not provide a way to receive Wheel
events. But the window decoration needs to pass wheel events on
the titlebar to KWin core.

In order to process also Wheel Events in Aurorae an event
filter is installed on the widget and in case the mouse positon
is on the title bar the titlebarMouseWheelOperation is invoked.


FIXED-IN: 4.9.1
REVIEW: 105801