Also backtracked the removal of wesnoth.get_recall_units, which is now available as wesnoth.units.find_on_recall - it's just more convenient than passing x=recall to wesnoth.units.find
wesnoth.current.event_context might not contain all information if the die event was triggered by wml ([fire_event]), this made wesnoth.get_unit error (invalid argument)
this has 2 advantages:
1) It decreased savefile size since the event is no longer sotred in
each savefile.
2) The ABILITY_FEEDING no longer assumes its used from within
[abilities]
