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
cast setsocktopt and getsockopt calls to fix windows build
ifdef to handle getsockopt format requirements on windows
Merge branch 'master' of https://github.com/highfidelity/hifi
wait on broadcastThread before destroying AvatarMixer, closes #2499
Merge pull request #2503 from birarda/master

increase NodeList send buffer size to 1MB