Release 1.8.6
Sync with Upstream Alchemy

Changes LLEnvManagerNew::setRegionChangeCallback to LLAgent::addRegionChangedCallback
Cleans up some of the timeout policies that aren't necessary any longer.
Modernizes parts of LLViewerKeyboard, updates llregistry.h
Begins changeover from LLDynamicArray to std::vector
Minor merge of newer, trivial SSA functions.
Introduces LLAgent functions: addParcelChangedCallback and canJoinGroups
Support for secondlife:///app/appearance SLapps.
Cleans up older functions.
Modernize LLSingleton
Fix Issue 1653: Using Search Box causes crash