Added function to get public and private key from Tox object.
Updated download page link.
Fixed possible threading issues.

send_lossy_cryptpacket() can get called from another thread meaning
the connection can be killed while the packet is sending.
Adding a new connection while a lossy packet is being sent could
also cause thread related issues.
decode video on separate thread
fix test
fix initialization order
audio/video decoding on separate thread with a queue
Merge branch 'notsecure-split-video'
Disable decode deadline, fixed build error.
Added userdata pointer to audio/video callbacks
Merge branch 'mannol1-master'
Increase dequeue queue size to 16 to prevent stuttering.