Copter: cancel takeoff if mode changed

ArduCopter/flight_mode.pde

@@ -234,7 +234,10 @@ static void exit_mode(uint8_t old_control_mode, uint8_t new_control_mode)
         // this assumes all manual flight modes use get_pilot_desired_throttle to translate pilot input to output throttle
         set_accel_throttle_I_from_pilot_throttle(get_pilot_desired_throttle(g.rc_3.control_in));
     }
-    
+
+    // cancel any takeoffs in progress
+    takeoff_stop();
+
 #if FRAME_CONFIG == HELI_FRAME
     // firmly reset the flybar passthrough to false when exiting acro mode.
     if (old_control_mode == ACRO) {

ArduCopter/takeoff.pde

@@ -61,6 +61,13 @@ static void takeoff_timer_start(float alt)
     takeoff_state.time_ms = (alt/takeoff_state.speed) * 1.0e3f;
 }
 
+// stop takeoff
+static void takeoff_stop()
+{
+    takeoff_state.running = false;
+    takeoff_state.start_ms = 0;
+}
+
 // update takeoff timer and stop the takeoff after time_ms has passed
 static void takeoff_timer_update()
 {