guided altitude targets are converted to alt-above-home
remove unnecessary fence_status local variable from guided_set_destination methods
log failures to set guided target under a new failure code: ERROR_CODE_DEST_OUTSIDE_FENCE (5)
rename pv_get_home_destination_distance_mc to pv_distance_to_home_cm
The new function can deal with a variable number of function parameters.
Additionally, I renamed the functions to norm(), because this is the
standard name used in several other projects.