do not use changed signal in disco: when we write some thing this signal is...

do not use changed signal in disco: when we write some thing this signal is emited each time we add / remove a character, so gajim sends many useless requiest

Plz do not use glade 2.10: pygtk2.6 is really not needed atm, and many people don't have it so we must not depend on pytgk2.6 fot the moment