* due to server bugs, some offline buddies are still notified on publication,
  causing error reply, that pep accepts as event. check message type/presence of error tag.
* check input/output for validity, where applicable
* extract common code into one place
* add avatar
  * pep_avatar, avatar_cache, avatar, aavatar (separate)
    *       hook_avatar_metadata_in                               @ pep_avatar  
          | hook_avatar_need_data_in (or symbol-resolved request) @ avatar_cache  
          V hook_avatar_data_in                                   @ pep_avatar  
            hook_avatar_in                                        @ avatar_cache
    * (!!!) how to handle outgoing event? what and where should do what?
  * handle url avatars (curl)
  * report absence of avatar