add back selective inclusion of Avatars based on distance
add a mutex to NodeData and leverage in AvatarMixer threads
add mutex header to NodeData
Merge pull request #2498 from birarda/master

fix thread contention and reinstate distance based avatar-mixer sending
Display warning popup when something went wrong with the fst upload
increase NodeList send buffer size by default to 128KB
output old size when notifying for send buffer size change
attempt to set send buffer size to 1MB
add a method to Agent for last read frame loudness
cast setsocktopt and getsockopt calls to fix windows build
Added mono to stereo conversion to fix Linux audio.  Closes #2508.
ifdef to handle getsockopt format requirements on windows
Merge pull request #2510 from birarda/agent-loudness

add a method to Agent for last read frame loudness
added more performance stats tracking to octree server
add a button on DS admin page to kill all nodes
Merge branch 'master' of https://github.com/highfidelity/hifi
Merge pull request #2513 from ey6es/master

Added mono to stereo conversion to fix Linux audio.  Closes #2508.
Merge pull request #2514 from birarda/kill-node-button

add a button on DS admin page to kill all nodes
wait on broadcastThread before destroying AvatarMixer, closes #2499
moved stopTrackingThread() to setIsShuttingDown() to reduce chance of object conflict