Add-ons Conversation Improvements by Xon 2.4.6

• Require XenForo 2.2+
• Improve handling of leaving/joining conversation and the impact on search.
  This will require re-indexing conversation messages.
  • When a user joins a conversation, ensure they can search that conversation
  • If a user leaves a conversation, do not return it in search results.

• Code style cleanup
• Use strict equality checks
• Force global namespace for functions which are known to be optimizable to bytecode in php