add extra PID option adafruit#113

Author: ladyada

boards.txt

@@ -26,6 +26,8 @@ adafruit_feather_m0.vid.0=0x239A
 adafruit_feather_m0.pid.0=0x800B
 adafruit_feather_m0.vid.1=0x239A
 adafruit_feather_m0.pid.1=0x000B
+adafruit_feather_m0.vid.2=0x239A
+adafruit_feather_m0.pid.2=0x0015
 adafruit_feather_m0.upload.tool=bossac
 adafruit_feather_m0.upload.protocol=sam-ba
 adafruit_feather_m0.upload.maximum_size=262144