mega2560 target and build optimizations
NOTES
added definitions from stk500boot, renamed functions to be similar to the rest of the code
variable names, address_t typedef for big progmems
function names, moved serial polling to serial.c
strict prototypes
removed unneeded code from stk500boot.c, added header file
added pin definitions for ATmega2560
serial function names, removed old debugfing definitions
strict prototypes
new serialPoll and stk500boot include
renamed mega2560 target to atmega2560
rebuilt images to the latest changes. Most likely will not work at all. UNTESTED\!\!\!