No functional change
eclipse stops complaining if no-break is used in place of fall-through

Using a global .dir-locals.el file is a better alternative than
reincluding the same emacs header in every file of the project.

This fixes the fixed wing behaviour of LOITER mode whne
Q_GUIDED_MODE=1.

Many thanks to the PertUAV team for finding and reporting this bug

Revert "ArduPlane: Convert references to AP_Airspeed.  Added automatic migration of ARSPD_FBW_MIN and ARSPD_FBW_MAX (plane parameter) to ARSPD_FBW_MIN and ARSPD_FBW_MAX (library parameter)."

This reverts commit da1b18d9.

ArduPlane: Convert references to AP_Airspeed.  Added automatic migration of ARSPD_FBW_MIN and ARSPD_FBW_MAX (plane parameter) to ARSPD_FBW_MIN and ARSPD_FBW_MAX (library parameter).

- outside this radius of a loiter waypoint is where crosstracking is available

this prevents a switch to AUTO from using VTOL mode incorrectly

this distinguishes between VTOL and fixed wing loiter targets

this allows you to do hybrid VTOL and fixed wing guided mode

Further to refactor of RC_Channel class which included
adding get_xx set_xx methods, change reads and writes to the public members
to calls to  get and set functionsss

old public member(int16_t)   get function -> int16_t     set function (int16_t)
(expression where c is an object of type RC_Channel)
c.radio_in                     c.get_radio_in()           c.set_radio_in(v)
c.control_in                   c.get_control_in()         c.set_control_in(v)
c.servo_out                    c.get_servo_out()          c.set_servo_out(v)
c.pwm_out                      c.get_pwm_out()            // use existing
c.radio_out                    c.get_radio_out()          c.set_radio_out(v)
c.radio_max                    c.get_radio_max()          c.set_radio_max(v)
c.radio_min                    c.get_radio_min()          c.set_radio_min(v)
c.radio_trim                   c.get_radio_trim()         c.set_radio_trim(v);

c.min_max_configured() // return true if min and max are configured

Because data members of RC_Channels are now private and so cannot be written directly
 some overloads are provided in the Plane classes to provide the old functionality

new overload Plane::stick_mix_channel(RC_Channel *channel)
which forwards to the previously existing
void stick_mix_channel(RC_Channel *channel, int16_t &servo_out);

new overload Plane::channel_output_mixer(Rc_Channel* , RC_Channel*)const
which forwards to
(uint8_t mixing_type, int16_t & chan1, int16_t & chan2)const;

Rename functions

 RC_Channel_aux::set_radio_trim(Aux_servo_function_t function)
    to RC_Channel_aux::set_trim_to_radio_in_for(Aux_servo_function_t function)

 RC_Channel_aux::set_servo_out(Aux_servo_function_t function, int16_t value)
    to RC_Channel_aux::set_servo_out_for(Aux_servo_function_t function, int16_t value)

 Rationale:

        RC_Channel is a complicated class, which combines
        several functionalities dealing with stick inputs
        in pwm and logical units, logical and actual actuator
        outputs, unit conversion etc, etc
        The intent of this PR is to clarify existing use of
        the class. At the basic level it should now be possible
        to grep all places where private variable is set by
        searching for the set_xx function.

        (The wider purpose is to provide a more generic and
        logically simpler method of output mixing. This is a small step)

- this is to allow min groundspeed to be enforced which is otherwise lost when TECS assigns a target airspeed at the lower level

also allows guided to change loiter directions

- except loiter_unlim which uses RTL_loiter, although I'm not sure why.

this allows the loiter radius for RTL to be controlled separately from
the radius for loiter (as requested by a user)

There is no crosstrack concept in the loiter navigation so when going from waypoint to loiter you will not converge onto the line between those two points. This commit adds crosstracking by performing normal waypoint navigation until you get near it.

this prevents us over-rolling in FBWA

this should produce better glide slopes when the aircraft is off
course