xflock4 has no usage/man page, "xflock4 -h" doesn't work

Even though xflock4 appears to not have any additional options that should be stated in its usage/man page, which appears to not exist. Even if no proper manpage is written, xflock -h should return some description rather than actually lock the screen.

Also, if an option is not implemented, xflock4 should complain about unknown argument and not just execute the action as it does now.