Implement Autohold button via custom skin

Allow auto holding buttons when pressing more then 1sec. Autohold is
applied when releasing the button and notified by a vibration and a mask
drawn over the autohold button.

Here's a custom skin exemple for mario kart implementing autohold on Z
and A buttons (small screens only):

http://dl.dropbox.com/u/27654797/Skin_Mario_kart.zip