So, it seems gtkconv checks on stuff in the prpl struct. The lack of
add_buddy in AIM and MSN disabled the Conversation->Add menu item.
Found by deryni.
[Desktop Entry]
_Name=Pidgin Internet Messenger
_GenericName=Internet Messenger
_Comment=Chat over IM. Supports AIM, Google Talk, Jabber/XMPP, MSN, Yahoo and more