MODIFIED: del_assoc/4 is now semidet as the documentation already stated, i.e., it _fails_ if the key does not appear in the input assoc.  Consistent with SICStus avl_delete/4 and YAP del_assoc/4.  Reported by Roberto Bagnara.
MODIFIED: del_assoc/4 is now semidet as the documentation already stated,
i.e., it _fails_ if the key does not appear in the input assoc.  Consistent
with SICStus avl_delete/4 and YAP del_assoc/4.  Reported by Roberto Bagnara.

edechter/swipl-devel,edechter/swipl-devel,edechter/swipl-devel,edechter/swipl-devel,edechter/swipl-devel