Per-protocol account settings names

[Sadrul Habib Chowdhury]

* Sergey Rudchenko had this to say on [02 Sep 2008, 08:52:43 +0300]:
> I also propose to implement
> validate_login function in the PurplePluginInfo to prevent user from
> enetering an incorrect text to the editbox.
>

That sounds like a good idea to me. I think a number of protocols (e.g.
OSCAR, XMPP, IRC, Yahoo! etc.) can use some sort of screenname
validation.

Sadrul