Add local patches to support the ATmega256x controller family that
features a 3-byte PC. patch-atmega256x-binutils is Bjoern Haase's
backported binutils patch for the ATmega256x (stripped down to those
GNU binutils directories that are present in the GDB source tree),
while patch-atmega256x-gdb is my own one to modify the AVR backend in
GDB to understand 3-byte PCs.
