Added some safeguards against crashes.
Updated group invite callback function signature.
Added error messages  when group chat invites fail.
Prevent crash when twc_chat_new returns NULL.
Implemented /group create.
Create group chat buffer if it's missing in namelist callback.
Use group chat title instead of "Group Chat #" if possible.
Prevent crashes in twc_chat_refresh.
Implemented /topic.
Added group chat title callback.
Formatting.