AVR core version bump

Author: Federico Fissore

hardware/arduino/avr/platform.txt

@@ -6,7 +6,7 @@
 # https://github.com/arduino/Arduino/wiki/Arduino-IDE-1.5---3rd-party-Hardware-specification
 
 name=Arduino AVR Boards
-version=1.6.6
+version=1.6.7
 
 # AVR compile variables
 # ---------------------