Stop focusbox movement on button mouseout

If a user presses the focusbox '+' button (generating a mousedown event, thus sending a 1 to the motor) and then drags the cursor out of the button, he does not generate a mouseup event, so the motor never gets reset to 0. That's bad. I circumvent this by adding a mouseout event to the button, namely the same event as the mouseup event. This will cause also events when just hovering over the button, but sending many 0's to the motor does not do any harm (checked with Paul).