Log Message:
Update chat/ejabberd to 16.04.

API Commands
- Add API versionning
- Changed error handling, based on exception
- ejabberd Command bugfixes
- Accept commands: add_commands syntax (along commands: –
  add_commands)
- Fix mod_muc_admin:get_room_options and set_room_affiliation
- mod_http_api: support 'open' ejabberd commands

Databases
- Split modules DB specific code into separate modules
- Rename "odbc" to "sql" everywhere
- Rename "internal" auth to "mnesia"
- Improve detection of databases supported by modules
- Switch to varchar(64) in mysql user.server/salt as text can't
  have default values
- 'serverkey' and 'salt' should have empty string as default

XMPP
- Drop headline messages sent to offline resources
- Don't omit bounces for messages of type "result"
- Match namespace when checking for chat states
- Fix check for standalone chat state notifications
- Disable TLS compression for s2s by default
- Make sure that ejabberd_sm sid are unique
- Send stream trailer at the very end of the processing
- Generate shorted jid for anonymous connections
- Fix anonymous SASL auth

ejabberdctl
- Add option to migration script to delete data from a table after
  they have been successfully moved to SQL database: ejabberdctl
delete_mnesia example.org
- Remove useless variable and quote EPMD and SPOOL_DIR
- Fix node ping command
- Use UUID for ctl node name
- Remove --auth in ejabberd_ctl.erl as it's useless, still
  useful for mod_rest
- Force ERL_PATH for Elixir console

Pubsub
- Fix use of pubsub node plugin when configured with
  default_node_config
- Set default value for pubsub#itemreply option
- Add subscribe/unsubscribe hooks

Internal
- Add mod_mam header file
- Replace ?ERR_* macros with ?ERRT_*
- change mod_ping Timers using maps instead of dict

Dependencies
- Update p1_utils to 1.0.4: Adds p1_time_compat:unique_timestamp()
- Update fast_tls to 1.0.3: Prevent buffer overflows and
  allocation failures
- Update stringprep to 1.0.3: Fix compilation on Windows and error
  message
- Update stun to 1.0.3: Use fast_tls 1.0.3
- Update esip to 1.0.4: Use fast_tls 1.0.3