Why is GCompletion deprecated

[Xavier Claessens <xclaesse gmail com>]

Hello GLib devs,

I upgraded to latest glib, and I discover that GCompletion is now 
deprecated. Empathy was using it to complete the nickname when hitting 
TAB in chatrooms.

I see nothing to replace that API... am I supposed to copy/paste its 
code inside Empathy?!?

Is there a good reason to deprecated that code?!?

Regards,
Xavier Claessens.