Undocumented predicates

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

 cleanup_calls_to

 collect_calls_to(Arg1, Arg2)

 calls_to(Arg1)

 calls_to(Arg1, Arg2, Arg3)

 calls_to(Arg1, Arg2, Arg3, Arg4)

 calls_to_hook(Arg1, Arg2, Arg3, Arg4)