disallow sort constraints in primitive Theory.add_axiom/add_def -- handled in Thm.add_axiom/add_def;

added Term.fold_atyps_sorts convenience;

moved Drule.forall_intr_frees to Thm.forall_intr_frees (in more_thm.ML, which is loaded before pure_thy.ML); discontinued old-style Theory.add_defs(_i) in favour of more basic Theory.add_def; modernized PureThy.add_defs etc. -- refer to high-level Thm.add_def;