Log Message:
chat/ejabberd: Update to 18.06.

Admin
- Stop ejabberd initialization on invalid/unknown options
- Add new options for OOM watchdog: oom_watermark and oom_queue
- Add ability to modify version string
- Add option ext_api_headers to define REST API custom headers
- Fix Erlang limits in ejabberdctl.cfg.example to reflect current
  situation
- Make trusted_proxied ejabberd_http option accept ip masks
- Teach acl ip matching about ipv4 mapped ipv6 addresses
- Removed watchdog_admins option from config, as has no effect anymore
- Improve logging of external authentication failures
- ejabberd_auth: Don't use cache if the option is disabled
- Make connected_users_info and user_sessions_info DB-agnostic

Core
- Support SASL PLAIN by xmpp_stream_out
- Add Resource Binding support to xmpp_stream_out
- Improve robustness of external authentication backends
- Don't use 'unsupported-version' inside SM element
- Generate SASL failures on unencrypted connections only for s2s
- Fix reset_stream in websocket using pre-rfc protocol
- Don't crash in bosh when we receive request with RID < prev_rid
- Get rid of all calls to jlib.erl module
- Support IPv6 connections for PostgreSQL, MySQL and LDAP
- Fix authentication for usernames containing uppercase characters
- Optimize HTTP requests memory usage
- PKIX: Just warn instead of ignore a certificate containing no domain
  names
- PKIX: Don't replace valid certificates with invalid ones

Modules
- Log modules startup
- mod_disco: Advertise disco#info and disco#items features
- mod_irc: is moved away from ejabberd repo to ejabberd-contrib
- mod_mam: Don't replace existing stanza ID
- HTTP upload: Generate HTTP Upload form using xdata codec
- HTTP upload: Improve error formatting
- HTTP upload: Return detailed error if HTTP upload is too large

MUC
- Always display room's xdata in disco#info
- Display muc#roomconfig_changesubject in room's disco#info
- Render roomname, allowinvites and allowpm in room disco#info
- Support for roomconfig_lang/roominfo_lang
- mod_muc_sql: Fix export to SQL

Push
- Omit summary for outgoing messages
- Further improve handling of carbons
- Also include sender/body for carbons
- Include a static body text by default
- keepalive: Increase default timeout to 3 days
- SQL: Check 'max_user_sessions' limit