Plane: emit throttle armed and throttle disarmed statustexts

ArduPlane/system.cpp

@@ -472,6 +472,9 @@ bool AP_Arming_Plane::arm(const AP_Arming::Method method, const bool do_arming_c
     }
 
     change_arm_state();
+
+    gcs().send_text(MAV_SEVERITY_INFO, "Throttle armed");
+
     return true;
 }
 
@@ -506,5 +509,7 @@ bool AP_Arming_Plane::disarm(void)
     }
 #endif
 
+    gcs().send_text(MAV_SEVERITY_INFO, "Throttle disarmed");
+
     return true;
 }