[imp] Hook - translate char /create username from full email.

[Otto Stolz]

PS.

I have written:
> - If it is invoked as _imp_hook_vinfo('vdomain'),
>    it is supposed to yield a domain string to be placed in the
>    input form next to the Username field.

You will see the effect of this invocation only if
you choose, in the Login form, another server (but
do not enter a username), and then hit "Login".

Cheers,
   OS