If an edit tool like `Crop` or `Red Eye Reduction` is active, zooming
by mouse wheel does not work. This is caused by the `QEvent::accepted`
flag set to `true` by default and therefore not propagating the event.
This patch clears the `accepted` flag for mouse wheel events until
a subclass of `AbstractRasterImageViewTool` will accept wheel events
by itself.
FIXED-IN: 18.08.0