Log Message:
Update ejabberd to 15.02.
Enable odbc, mysql and pgsql support unconditionally (no dependency cost).

Changes in 15.02:
- Add Elixir support, allows to write plugins in Elixir (not enabled in
  this pkgsrc package)
- New command to reload configuration without restart
- Support old style erlang expressions in YAML configuration
- Improved captcha listener parsing when protocol not specified
- Fix upgrade of old unbinarized pubsub table from 2.1
- Minor updates in the documentation
- Other bugfixes