New extban that match unidentified users that not match a usermask

[danilomac]

It would be helpful to ban spambots without affect some legit unidentified users.

Spambots usually are not registered and don't use gateways, so we can ban all unidentified users that not use a gateway. If we call that new extban $e, so +b $e:*!*@gateway/* would ban ever unidentified user that not fit *!*@gateway/*.

And it can be also used when we want to ban unregistered users but we know some IP range or domain that is safe.

[danilomac]

I think it is also a good idea an extban to unidentified users that does match a usermask, to set some wide ban to unidentified as alternative to ban all unidentified. If we call that extban $u, +b $u:*!~*@* would ban unidentified users that don't use Ident.