Incorporated onion into Tox.

Fixed a couple of issues related to that.
Onion servers are now DHT ready.
Small performance increases.
Fixed segfault.
Some optimizations and fixes.
Added no_replay and added some things to the docs.
Small protocol change for more replay attack prevention.

see the changes to Prevent_Tracking.txt
Commented out now useless code.
Some small improvements added.
Fixed onion_test.
Merge pull request #691 from benwaffle/master

fixed MSWindows detection in network.h
Update network.c
Merge pull request #692 from benwaffle/patch-1

Update network.c
Fakeid packets are now also sent via the DHT.
Merge branch 'onion'
Enabled onion in bootstrap_serverdaemon.
Fixed missing cleanup
Moved things around
Merge pull request #693 from nurupo/dht_bootstrap_daemon

Fixed missing cleanup
Updated DHT server list with onion supporting DHT servers.

Onionised DHT_test.