Pair-Programmed-With: Randy Mackay <rmackay9@yahoo.com>

per Randy's suggestion, fast_atan2() is no longer necessary over atan2() because only copter uses it and copter is no longer supported on future builds of APM

https://github.com/Airphrame/ardupilot/commit/ccd578664ffdb5998d2655bd020ae48e7ea628de#commitcomment-11025083

Also update function description

Use default position when waypoint lat/lon are zero,
and default altitude when waypoint alt is zero, for
both spline and straight-line waypoints.

Fixes #1145.

home has moved to ahrs
saves 15 bytes of RAM

removed pv_latlon_to_vector, pv_get_lat, pv_get_lon.
it would probably be best if these were moved into the Math library

value

this is more efficient than passing a whole structure on the stack

Pair-Programmed-With: Brandon Jones <brnjones@gmail.com>