Elgg/Elgg — pull request #6789 by jeabakker (2014-04-25 11:59:25+00:00)
Title: chore(upgrade): enable site_notifications

when upgrading from elgg 1.8 to elgg 1.9 the site_notifications plugin
takes over the 'site' notification from the messages plugin. So enable
this new plugin if the messages plugin was enabled

Fixes #6468