Arduino Leonardo support

[OttoHermansson]

I have been working on a small custom commander that uses a Arduino pro micro witch is based on the leonardo. To get it to work the code needs a small update. All that is needed is to change one line of code in "DCCHardware.c" to add definition of ATmega32U4.

Change line 77 from:

#if defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__) || defined(__AVR_AT90CAN128__) || defined(__AVR_AT90CAN64__) || defined(__AVR_AT90CAN32__)

to:

#if defined(__AVR_ATmega32U4__) || defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__) || defined(__AVR_AT90CAN128__) || defined(__AVR_AT90CAN64__) || defined(__AVR_AT90CAN32__)