Summary of significant changes:
-Autsave doesn't depend on STREAM_EXTRA3
-Don't risk only saving one compass on copter if CAL_ALWAYS_REBOOT is set
-Only calibrate compasses that are both health and marked for use (there was a inconsistency in handling the mask)
-Fix incorrect failure reporting on DO_ACCEPT_MAG_CAL with a mask of 0 if a channel was specifically not started
-Fix not starting the buzzer if the delay is set to 0 seconds
-Always send MAG_CAL_REPORT until its acknowledged
-Correct the field in MAG_CAL_REPORT for autosave to indicate if the compass had actually been saved, rather then being scheduled to be saved
-Remmove unused public interfaces
In addition:
- bbbmini, navio and navio2 can force HMC5843 backend to
be external.
- there was a typo in the backend name that's now fixed:
AK8953 vs AK8963
These are not used. The only place where raw fields are used are in the
compass calibrator and we don't need to store them.
Additionally remove duplicated documentation about the meaning of the
functions to avoid them getting out of sync.