Log Message:
Update ejabberd to 2.1.9.

Changes:

* Core ejabberd
- Decrease CPU usage caused by tls:send with large data
- Escape iolist correctly when NIFs are disabled (EJAB-1462)
- Fix code to satisfy Dialyzer warnings
- Fix compilation in Windows
- Replace calls of OTP’s Binary, since they would require R14

* LDAP
- Document ldap_tls_cacertfile and ldap_tls_depth options (EJAB-1299)
- Log an error when an LDAP filter is incorrect (EJAB-1395)
- New options: ldap_tls_cacertfile and ldap_tls_depth (EJAB-1299)
- New option: ldap_deref_aliases (EJAB-639)
- Match ldap_uidattr_format case-insensitively (EJAB-1449)

* MUC
- Support for multiple entry with same nick to MUC rooms (EJAB-305)
- Support voice request and approvement
- New room option: allow_private_messages_from_visitors
- New room options: allow_voice_requests and voice_request_min_interval
- Include status 110 in presence to new occupant (EJAB-740)
- Fix mod_muc_log crash when first log entry is room destroy (EJAB-1499)
- Many fixes and improvements in mod_muc

* Pubsub
- Enable pubsub#deliver_notification checking (EJAB-1453)
- Fix Denial of Service when user sends malformed publish stanza (EJAB-1498)

* ODBC
- Fix ODBC account counting (EJAB-1491)
- Optimized mod_roster_odbc:get_roster

* Miscellanea:
- New SASL SCRAM-SHA-1 authentication mechanism (EJAB-1196)
- New option: resource_conflict (EJAB-650)