Copter: clear thr accel I term on take-off

ArduCopter/ArduCopter.pde

@@ -1977,6 +1977,12 @@ void update_throttle_mode(void)
         if(ap.auto_armed) {
             // alt hold plus pilot input of climb rate
             pilot_climb_rate = get_pilot_desired_climb_rate(g.rc_3.control_in);
+
+            // clear i term when we're taking off
+            if (pilot_climb_rate > 0 && ap.land_complete) {
+                set_throttle_takeoff();
+            }
+
             if( sonar_alt_health >= SONAR_ALT_HEALTH_MAX ) {
                 // if sonar is ok, use surface tracking
                 get_throttle_surface_tracking(pilot_climb_rate);    // this function calls set_target_alt_for_reporting for us

ArduCopter/Attitude.pde

@@ -859,6 +859,14 @@ void throttle_accel_deactivate()
     throttle_accel_controller_active = false;
 }
 
+// set_throttle_takeoff - allows parents to tell throttle controller we are taking off so I terms can be cleared
+static void
+set_throttle_takeoff()
+{
+    if (g.pid_throttle_accel.get_integrator() < 0)
+        g.pid_throttle_accel.reset_I();
+}
+
 // get_throttle_accel - accelerometer based throttle controller
 // returns an actual throttle output (0 ~ 1000) to be sent to the motors
 static int16_t