Undocumented predicates

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

 attach_prefix(Arg1, Arg2, Arg3)

 complete_args(Arg1, Arg2, Arg3)

 optimize_call_N(Arg1, Arg2)

 slim_goal(Arg1, Arg2)

 subtree(Arg1, Arg2, Arg3, Arg4)

 subtree(Arg1, Arg2, Arg3, Arg4, Arg5)

 reduce(Arg1, Arg2, Arg3)

 reduce(Arg1, Arg2, Arg3, Arg4)

 reduce_one(Arg1, Arg2, Arg3, Arg4)

 term_rewrite(Arg1, Arg2, Arg3)

 term_rewrite(Arg1, Arg2, Arg3, Arg4)