Undocumented predicates

The following predicates are exported, but not or incorrectly documented.

 foreign(Arg1)

 foreign(Arg1, Arg2)

 foreign_spec(Arg1)

 native(Arg1)

 native(Arg1, Arg2)

 normalize_ftype(Arg1, Arg2)

 normalize_ftgen(Arg1, Arg2)

 fimport(Arg1)

 fimport(Arg1, Arg2)

 nimport(Arg1)

 nimport(Arg1, Arg2)

 int64(Arg1)

 lang(Arg1)

 long(Arg1)

 returns(Arg1, Arg2)

 parent(Arg1, Arg2)

 returns_state(Arg1)

 memory_root(Arg1)

 ptr(Arg1)

 ptr(Arg1, Arg2)

 array(Arg1, Arg2, Arg3)

 setof(Arg1, Arg2)

 float_t(Arg1)

 size_t(Arg1)

 tgen(Arg1)

 tgen(Arg1, Arg2)

 dict_t(Arg1, Arg2)

 dict_t(Arg1, Arg2, Arg3)

 dict_join_t(Arg1, Arg2, Arg3, Arg4)

 dict_extend_t(Arg1, Arg2, Arg3, Arg4)

 join_dict_types(Arg1, Arg2, Arg3, Arg4, Arg5, Arg6)

 join_type_desc(Arg1, Arg2, Arg3, Arg4)