Log Message:
Update chat/ejabberd to 17.11.

New features
- ACME Support
- Introduce 'certfiles' global option
- Use new API for IQ routing

Admin
- Omit "ProtectSystem" option from systemd unit
- Log warnings for c2s/s2s certfile option
- Log a message when a user gets registered
- ejabberdctl: Fix 'read' syntax for non-bash shells
- Fix renew_certificates ejabberdctl command
- Unregister commands when stopping node only if it's last one
- Halt ejabberd if the top supervisor fails to start

Build
- Avoid badarg error when running get-deps before ./configure has
  created src/ejabberd.app
- Fix sed invocation that was incompatible with FreeBSD's sed
- Makefile.in: Fix "make clean && make"
- Improve --enable-system-deps
- Install binaries with 755 permissions
- Install eimp binary with +x attribute
- Remove find-outdated-deps script, we have better replacement for it

Databases
- Allow export command regardless of the configured db_type
- Add SQL_INSERT macro and update SQL queries to use server_host field
- Update SQL archive index to match mysql.sql
- mod_muc: Use correct table field name in sql query

MAM
- Always strip stanza IDs
- Announce support for stanza IDs
- Don't store from 'sm_receive_packet' hook
- Fix mod_mam reloading
- Ignore non-message stanzas earlier
- Improve handling of forked messages
- Make sure a stanza ID is always added
- Make sure archived message isn't bounced
- Prepare version 0.6.1 of XEP-0313 (MAM) support

MUC
- Properly store subject element
- Resend presences and history if presence possesses x MUC element
- Send presence-unavailable when expulsing a participant
- Add mucsub event for subscribers list changes
- Optimize muc subscriptions handling
- Show real jid in mucsub subscription change events

PubSub
- Add basic PubSub meta-data support
- Rewrite pubsub export to sql
- Cleanup tree requests, rename pubsub_node.type to pubsub_node.plugin
- Fix select_type race on plugin_init
- Implement parentnodes seek for hometree
- Delete cached item on node removal
- Fix delete item from unregistered user
- Cleanup pubsub subscriptions quering, fix pep case
- PEP services must send notifications to the account owner

Push
- Avoid notification duplicates
- Add support for SQL storage
- Add export from Mnesia database to SQL file
- Don't store xdata() in Mnesia table
- Simplify backend interface