The LED_GREEN is actually off of PORTD.2, and so in arduino this is
Digital Pin "2". Also added/adjusted comments on the #defines for board
revs to include "PTH" and "SMD" and additional date codes.
Button checking is now faster, more responsive, and should handle heavy,
slow button presses as well. Now works fully under Arduino v1.0 and have
removed the majority of the older C specific code.