Mighty-1284P core updated for Arduino 1.0.6

Constantin:
You guys are amazing. I started using the 1284p a few years back before switching most of my work to Teensy. However, some things are better done on an AVR, and the 1284p is perfect for my latest project, monitoring a multitude of 1-wire devices. Thank you for updating the core/board/etc files to make it possible!!!

Just to note that development is still continuing with support recently added for the 1.6.x IDEs. I've created a new thread just for the 1.6.x updates:

Mighty-1284p repo updated for IDE 1.6.x