these will be back in 2.74

these are not use anymore, as voltage_average() is used instead

needed for different analog input scaling

this fixes it on PX4

this allows it to work on PX4

this is for ratiometric sensors such as the 3DR airspeed sensor and
the Maxbotix analog sonar

If WP A and B were the same or ground speed was exactly zero, then the
previous code would produce a nan output.  Protection against these
two cases has been added.

If WP A and B are equal, we track directly to the target waypoint

Also smooth RTL's initial climb stage by projecting stopping point

We do not want people modifying the COMPASS_MOTCT manually

Perhaps easier to understand if we use the "nav" and "conditional"
command labels

individual do_* commands are responsible for setting roll-pitch, yaw and
throttle modes.  Removing this redundant setting of the controllers
removes the short period (10th second max) where loiter and waypoint
controller's desired roll and pitch were used even before the
controllers have been run once.

This stops run-up in target position and nav controller I terms ahead of
throttle being raised

needed for new nuttx structure

Nose was only pointing home if your initial altitude was above the
RTL_ALT