title: Cocoa: distinguish input device / scrollWheel: as mouse-scroll wheel and TrackPad
body: <p>I am looking for a method to reliably distinguish within <code>[NSResponder scrollWheel:]</code> if the users input device has a one-dimensional scroll-wheel or a two dimensional trackPad/magicMouse?</p>
  
  <p>In the first I would like to implement a different behavior. 
  But just taking a look on the deltaX of the <code>NSEvent</code> would be a little weak.
  Any suggestions?</p>