The roster list is now split from MainWindow into RosterWindow, which
can be used arbitrarily for selecting something from contacts. The
im_what, title, and target can be specified.
Right now it's in use under the Chat menu, "New chat…". Chats can only
have two members (DM/PM), so "New chat…" directly leads to the roster
list.
In the future, roster list might be extended to allow specification of
non-contact users based on their identifiers, or filtering based on
protocol/account― this could help it with "invites" to future rooms,
etc.
IM_CREATE_CHAT and IM_CHAT_CREATED were also added to the protocol API,
allowing a new chat to be explicitly created from Caya or the protocol.
0326cee687