Copter: add comments to set_land_complete

ArduCopter/land_detector.cpp

@@ -79,6 +79,7 @@ void Copter::update_land_detector()
     set_land_complete_maybe(ap.land_complete || (land_detector_count >= LAND_DETECTOR_MAYBE_TRIGGER_SEC*MAIN_LOOP_RATE));
 }
 
+// set land_complete flag and disarm motors if disarm-on-land is configured
 void Copter::set_land_complete(bool b)
 {
     // if no change, exit immediately
@@ -94,6 +95,7 @@ void Copter::set_land_complete(bool b)
     }
     ap.land_complete = b;
 
+    // trigger disarm-on-land if configured
     bool disarm_on_land_configured = (g.throttle_behavior & THR_BEHAVE_DISARM_ON_LAND_DETECT) != 0;
     bool mode_disarms_on_land = mode_allows_arming(control_mode,false) && !mode_has_manual_throttle(control_mode);