Removed define that could become confusing.
Adding encrypted data to send/getnode packets part 1.
Added symmetric crypto functions to net_crypto.
Astyled some files.
Adding encrypted data to send/getnode packets now done.
Removed now useless ping_id from send/get node packets.
Fixed build error with libsodium.
Base of hardening stuff.
Added some hardening functions to test get nodes.
Removed some now useless code.
Merge branch 'master' into harden

Also removed some old, useless loading code.
Testing requests are now sent.
Get node testing response packets are now handled.
Merge branch 'master' into harden

Conflicts:
	toxcore/DHT.c
Added more printing to DHT_test, fixed typo.
Fixed small issues.

DHT_test now only prints non zero entries.
Fixed test.
Significantly trimmed down version of an ID<=>IP cache.
Besides acknowledging timeouts, the module isn't trying to do anything fancy with the data besides storing and retrieving.
Assoc's array is now allocated dynamically and per default much smaller (320 entries).
id_hash() was not at all working as expected for very small bucket size (when (size / 4) was zero). Simplified to be trivially correct.
Also added a used flag on adding an entry, which is set by callers if they have that association in active use. Those get priority over unused entries on collision.
Fleshed out test to be at least elementary useful.
Each group chat now uses an own, small assoc (80 entries).
Nodes now only send good nodes (or the node that was specifically asked for).