Add a way to abort a button press

[GwnDaan]

Naturally if I accidentally pressed a button, I'd try to abort the press with sliding my finger of the button and then releasing. It would be nice if we can implement such a behavior. Right now we always send an ButtonUnlatchedOrReleased if there is a button at the "mouse down" coordinates. Instead we should try to send a ButtonPressAborted when the "mouse up" coordinates is outside of the button initially pressed.