Added an interface for the listing of existing chatrooms
Several protocols can provide a list of existing chatrooms that a user
is able join. This is crucial for the usage of several protocols, most
notably Purple and Facebook.
Plugins wishing to support this extended functionality must implement
the new prpl->chat_list() function. This implemented function will in
most cases send a remote request for the list of chatrooms. Once the
list of chatrooms is obtained, a bee_chat_info_t GSList must be created
and assigned to the im_connection->chatlist field. Then a call to the
bee_chat_list_finish() is needed to display the list to the user.
The chat list is maintained entirely by the plugin, so it is important
to ensure all pointers related to the chat list remain valid until the
chat list is set to NULL. This list is used internally by bitlbee to
calculate indexes, which then allows the user to join a chat with an
index, rather than some random identifier. It also important to ensure
the list is properly freed whenever it is updated, or when the account
is disconnect via the prpl->logout() function.
On the user interface side of things, the 'chat list' subcommand was
recommissioned. For a user to list the existing chat rooms:
chat list <account id>
Afterwards a user can join a chatroom in the list with its index. This
extends the functionality of the 'chat add' subcommand by adding in
support for the exclamation point operator to denote an index.
chat add <account id> !<index> [channel]
