Arduino IDE Modification Procedure

1. Download 'XMega For Arduino' source
2. Apply 'patch.boards.txt' and 'patch.avrdude.conf'
   (Optionally you can manually modify them)
3. Create a symbolic link (or copy) the 'cores' and 'variants' trees from 'XMega For Arduino'
4. Apply patches for compilers and tools (including 'avrdude') as needed
   NOTE: this may require some significant effort on your part
5. Re-start the Arduino IDE. New board types should now be visible (and fully supported)