Plane: fixed places that assumed mission command IDs are 8 bit

ArduPlane/ArduPlane.cpp

@@ -485,7 +485,7 @@ void Plane::update_GPS_10Hz(void)
  */
 void Plane::handle_auto_mode(void)
 {
-    uint8_t nav_cmd_id;
+    uint16_t nav_cmd_id;
 
     // we should be either running a mission or RTLing home
     if (mission.state() == AP_Mission::MISSION_RUNNING) {

ArduPlane/Attitude.cpp

@@ -1176,7 +1176,7 @@ bool Plane::allow_reverse_thrust(void)
     switch (control_mode) {
     case AUTO:
         {
-        uint8_t nav_cmd = mission.get_current_nav_cmd().id;
+        uint16_t nav_cmd = mission.get_current_nav_cmd().id;
 
         // never allow reverse thrust during takeoff
         if (nav_cmd == MAV_CMD_NAV_TAKEOFF) {