ArduCopter: use FALLTHROUGH define

When falling through on a case switch, allow to add an empty statement
with the correct attribute to tell the compiler this behavior is
intended.

ArduCopter/commands_logic.cpp

@@ -748,14 +748,14 @@ bool Copter::verify_payload_place()
         // we're there; set loiter target
         auto_payload_place_start(wp_nav->get_wp_destination());
         nav_payload_place.state = PayloadPlaceStateType_Calibrating_Hover_Start;
-        // no break
+        FALLTHROUGH;
     case PayloadPlaceStateType_Calibrating_Hover_Start:
         // hover for 1 second to get an idea of what our hover
         // throttle looks like
         debug("Calibrate start");
         nav_payload_place.hover_start_timestamp = now;
         nav_payload_place.state = PayloadPlaceStateType_Calibrating_Hover;
-        // no break
+        FALLTHROUGH;
     case PayloadPlaceStateType_Calibrating_Hover: {
         if (now - nav_payload_place.hover_start_timestamp < hover_throttle_calibrate_time) {
             // still calibrating...
@@ -768,13 +768,13 @@ bool Copter::verify_payload_place()
         gcs().send_text(MAV_SEVERITY_INFO, "hover throttle delta: %f", static_cast<double>(hover_throttle_delta));
         nav_payload_place.state = PayloadPlaceStateType_Descending_Start;
         }
-        // no break
+        FALLTHROUGH;
     case PayloadPlaceStateType_Descending_Start:
         nav_payload_place.descend_start_timestamp = now;
         nav_payload_place.descend_start_altitude = inertial_nav.get_altitude();
         nav_payload_place.descend_throttle_level = 0;
         nav_payload_place.state = PayloadPlaceStateType_Descending;
-        // no break
+        FALLTHROUGH;
     case PayloadPlaceStateType_Descending:
         // make sure we don't descend too far:
         debug("descended: %f cm (%f cm max)", (nav_payload_place.descend_start_altitude - inertial_nav.get_altitude()), nav_payload_place.descend_max);
@@ -808,7 +808,7 @@ bool Copter::verify_payload_place()
             return false;
         }
         nav_payload_place.state = PayloadPlaceStateType_Releasing_Start;
-        // no break
+        FALLTHROUGH;
     case PayloadPlaceStateType_Releasing_Start:
 #if GRIPPER_ENABLED == ENABLED
         if (g2.gripper.valid()) {
@@ -823,7 +823,7 @@ bool Copter::verify_payload_place()
         gcs().send_text(MAV_SEVERITY_INFO, "Gripper code disabled");
 #endif
         nav_payload_place.state = PayloadPlaceStateType_Releasing;
-        // no break
+        FALLTHROUGH;
     case PayloadPlaceStateType_Releasing:
 #if GRIPPER_ENABLED == ENABLED
         if (g2.gripper.valid() && !g2.gripper.released()) {
@@ -831,24 +831,24 @@ bool Copter::verify_payload_place()
         }
 #endif
         nav_payload_place.state = PayloadPlaceStateType_Released;
-        // no break
+        FALLTHROUGH;
     case PayloadPlaceStateType_Released: {
         nav_payload_place.state = PayloadPlaceStateType_Ascending_Start;
         }
-        // no break
+        FALLTHROUGH;
     case PayloadPlaceStateType_Ascending_Start: {
         Location_Class target_loc = inertial_nav.get_position();
         target_loc.alt = nav_payload_place.descend_start_altitude;
         auto_wp_start(target_loc);
         nav_payload_place.state = PayloadPlaceStateType_Ascending;
         }
-        // no break
+        FALLTHROUGH;
     case PayloadPlaceStateType_Ascending:
         if (!wp_nav->reached_wp_destination()) {
             return false;
         }
         nav_payload_place.state = PayloadPlaceStateType_Done;
-        // no break
+        FALLTHROUGH;
     case PayloadPlaceStateType_Done:
         return true;
     default:

ArduCopter/control_autotune.cpp

@@ -183,7 +183,8 @@ bool Copter::autotune_init(bool ignore_checks)
         case AUTOTUNE_MODE_FAILED:
             // autotune has been run but failed so reset state to uninitialized
             autotune_state.mode = AUTOTUNE_MODE_UNINITIALISED;
-            // no break to allow fall through to restart the tuning
+            // fall through to restart the tuning
+            FALLTHROUGH;
 
         case AUTOTUNE_MODE_UNINITIALISED:
             // autotune has never been run

ArduCopter/navigation.cpp

@@ -40,7 +40,7 @@ void Copter::calc_wp_distance()
             wp_distance = wp_nav->get_wp_distance_to_destination();
             break;
         }
-        // no break
+        FALLTHROUGH;
     default:
         wp_distance = 0;
         break;
@@ -67,7 +67,7 @@ void Copter::calc_wp_bearing()
             wp_bearing = wp_nav->get_wp_bearing_to_destination();
             break;
         }
-        // no break
+        FALLTHROUGH;
     default:
         wp_bearing = 0;
         break;