allow only scrolling with horizontal "scroll wheel"

[Grienauer]

Using e.g a magic mouse has a "horizontal scroll wheel" and when scrolling down with the cursor over the overscroll element, prevents from scrolling the whole page, instead it scrolls the element to the left/right... It would be great to prevent horizontal scroll events when wheelDirection: 'horizontal' is set.

also the touchpad has this behavior, when using 2 fingers to scroll...
thx!