Sub: handle common GPS messages in base GCS_MAVLINK class

ArduSub/GCS_Mavlink.cpp

@@ -1713,6 +1713,11 @@ AP_Mission *GCS_MAVLINK_Sub::get_mission()
     return &sub.mission;
 }
 
+AP_GPS *GCS_MAVLINK_Sub::get_gps() const
+{
+    return &sub.gps;
+}
+
 AP_ServoRelayEvents *GCS_MAVLINK_Sub::get_servorelayevents() const
 {
     return &sub.ServoRelayEvents;

ArduSub/GCS_Mavlink.h

@@ -18,6 +18,7 @@ protected:
     AP_Mission *get_mission() override;
     AP_Rally *get_rally() const override;
     AP_ServoRelayEvents *get_servorelayevents() const override;
+    AP_GPS *get_gps() const override;
 
     uint8_t sysid_my_gcs() const override;