Modify avatar recommendations
test_avatars: Implement new policy for the user avatar file

Change location of the user avatar from "<data dir>/avatar.png" to
"<data dir>/avatars/<user id>.png", as proposed by commit
6f4ab49f5c2a33aab00bdb9e80dfe51624089899
Group chats now use friendcon_id instead of friendnumber.
Merge branch 'master' of https://github.com/irungentoo/toxcore
change avatar requirements
Fixed crash in tox_new().
Merge branch 'master' of https://github.com/dubslow/toxcore
Rework toxav/rtp.c to use ntohl/htonl and ntohs/htons

Now we can also remove the helper routines from toxcore/util.[ch].
Merge branch 'rework_av'
Added some functions to friend_connection.
Group chats now actually work somewhat.
del_groupchat and kill_groupchats now work properly.
If connection is already connected, send a online packet to it.
Removed useless code.
Peers now time out and delete themselves from group chats.

Some other work done.
People in groups can now be added/removed from friends list without issues.
Fixed tox_load() comment.
Implemented tox_callback_group_namelist_change callback in group chats.

No names yet though.
null terminate group messages (cause jfreegman can't str8 c)
Added name packet to group chats, send one when appropriate.