GCC/ATmegaxxxx port path and name change. (#51)

Moving ATmega port to third party directory, and mature it there. Once we are fully done, the port could then be moved back to portable/GCC. 
diff --git a/portable/GCC/ATmegaxxxx/port.c b/portable/ThirdParty/GCC/ATmega/port.c
similarity index 100%
rename from portable/GCC/ATmegaxxxx/port.c
rename to portable/ThirdParty/GCC/ATmega/port.c
diff --git a/portable/GCC/ATmegaxxxx/portmacro.h b/portable/ThirdParty/GCC/ATmega/portmacro.h
similarity index 100%
rename from portable/GCC/ATmegaxxxx/portmacro.h
rename to portable/ThirdParty/GCC/ATmega/portmacro.h
diff --git a/portable/GCC/ATmegaxxxx/readme.md b/portable/ThirdParty/GCC/ATmega/readme.md
similarity index 100%
rename from portable/GCC/ATmegaxxxx/readme.md
rename to portable/ThirdParty/GCC/ATmega/readme.md