Updated ArduinoCore, changed references to be dynamic.

I got few problems to compile it. First of them the ArduinoCore was out of date. It was using few deprecated things that didnt work my my avr-gcc (4.8.2), so I updated it.

Also the library path on Blink project was "hardcoded", I changed to a Eclipse Workspace path, so no matter where the ArduinoCore is, the project will compile. (if the ArduinoCore project is on workspace).

Works fine for me now, ATMEGA 1280. :)