Plane: removed unused prototypes

ArduPlane/Plane.h

@@ -1057,8 +1057,6 @@ private:
     void calc_nav_yaw_ground(void);
     void throttle_slew_limit(void);
     bool suppress_throttle(void);
-    void channel_output_mixer_pwm(uint8_t mixing_type, uint16_t & chan1, uint16_t & chan2)const;
-    void channel_output_mixer(uint8_t mixing_type, SRV_Channel::Aux_servo_function_t servo1, SRV_Channel::Aux_servo_function_t servo2);
     void channel_function_mixer(SRV_Channel::Aux_servo_function_t func1_in, SRV_Channel::Aux_servo_function_t func2_in,
                                 SRV_Channel::Aux_servo_function_t func1_out, SRV_Channel::Aux_servo_function_t func2_out);
     void flaperon_update(int8_t flap_percent);