Early re-implementation of announce packet

Major fuckup with crypto_sign not accepting crypto_box keys
new group chats specs
Longids: compiles and segfaults nicely

Reactivated signatures, few helper functions

Groupchat ids are mate by combining two keys
Working and tested signatures
Merge remote-tracking branch 'upstream/master' into gc_announce_api_change
Gephi version, yo
old group_chats functions were commented in messenger and tox. test for group_chats added
long_keypair function is added, some functions in new chats also
packet sizes
dark forces were very active, so to say...
Rewrote audio packet queue.

Audio killing itself after 20 minutes in a call should be fixed.
Merge branch 'master' of https://github.com/mannol1/toxcore
Increased default jitter buffer size by 1.
Fixed some issues with queue.

disconnecting then reconnecting right away should no longer kill
audio transmission.
Fixed crash.
Merge from upstream
Start sequence number at zero instead of one.
Make codec settings dynamic
Fixed tests and conflicts
Fixed buffer overflow