New syntax on message-IDs

[Julien ÉLIE]

> Is it OK for news servers to switch to the new USEFOR syntax right
> now?  or would it cause problems?
>
> We can use that new syntax, starting with INN 2.5.2.

It appears that it would not trigger any interoperability issue off.
Consequently, I have just committed the change.

innd and nnrpd now share the same syntax rules to validate
a message-ID.

-- 
Julien ÉLIE

« -- Comment s'appelle cette ville ?
  -- Divodurum.
  -- N'essaie pas de m'amadouer ! Non, je ne veux pas de rhum ! » (Astérix)