started work on sending nack packets from client
remove MMX math to fix stereo discrepancies
Merge pull request #2998 from birarda/master

remove MMX math in stereo audio copy
client-side nack sending complete; ready to test
added write lock/unlock

...for _octreeSceneStatsLock
added random packet drops; ready to test
Merge remote-tracking branch 'upstream/master' into packet_recovery_pull
packet recovery seems to be working

Seems to impact FPS a lot.  OctreeSceneStats is not being locked (causes
freezing, need to find out why).
removed interface print statements
added octree scene stats locking and unlocking
moved around code in sendNack() a bit
Merge branch 'packet_recovery_pull'