Send NOTICEs like private messages, instead of server messages, only if the biboumi user previously sent a message to that nick

If a biboumi user sends a private message to coucou%irc.example.com@biboumi.example.com, any future NOTICE from the “coucou” user should be sent from the coucou%irc.example.com@biboumi.example.com, instead of irc.example.com@biboumi.example.com like it is at the moment. Maybe also try to look for the “gone” chatstates, to reset that behaviour.

See the discussion with logicaldash Tue Jul 29 19:35:37 CEST 2014 on biboumi@muc.poez.io

(from redmine: created on 2014-07-29, closed on 2014-11-12)