[Serusers] No multiple registrations

[Alejandro Perez]

Hello.

	I've been browsing the mail list but don't seem to be able to find a method
to disable multiple callers from using the same login details.
	In other words, allowing only one registration for each user and disabling
the rest.

	I believe that Jan wrote a patch (for ver 0.8.10?) that did something
similar.

	Could anyone provide a pointer for this issue?

Thanks in advance.
Regards
Alex