AP_Vehicle: add set_target_posvel_NED method

libraries/AP_Vehicle/AP_Vehicle.h

@@ -183,6 +183,7 @@ public:
     */
     virtual bool start_takeoff(float alt) { return false; }
     virtual bool set_target_location(const Location& target_loc) { return false; }
+    virtual bool set_target_posvel_NED(const Vector3f& target_pos, const Vector3f& target_vel) { return false; }
     virtual bool set_target_velocity_NED(const Vector3f& vel_ned) { return false; }
     virtual bool set_target_angle_and_climbrate(float roll_deg, float pitch_deg, float yaw_deg, float climb_rate_ms, bool use_yaw_rate, float yaw_rate_degs) { return false; }