Undocumented predicates

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

 new_bvar(Arg1, Arg2)

 is_bvar(Arg1)

 b_put(Arg1, Arg2)

 b_get(Arg1, Arg2)

 new_nbvar(Arg1, Arg2)

 is_nbvar(Arg1)

 nb_put(Arg1, Arg2)

 nb_get(Arg1, Arg2)