Copter: give the AHRS access to the range beacon sensor

ArduCopter/system.cpp

@@ -188,6 +188,9 @@ void Copter::init_ardupilot()
      */
     hal.scheduler->register_timer_failsafe(failsafe_check_static, 1000);
 
+    // give AHRS the rnage beacon sensor
+    ahrs.set_beacon(&g2.beacon);
+
     // Do GPS init
     gps.init(&DataFlash, serial_manager);