(* saturate_term newmeta metasenv context ty *)
(* Given a type [ty] (a backbone), it returns its head and a new metasenv in *)
(* which there is new a META for each hypothesis, a list of arguments for the *)
(* saturate_term newmeta metasenv context ty *)
(* Given a type [ty] (a backbone), it returns its head and a new metasenv in *)
(* which there is new a META for each hypothesis, a list of arguments for the *)