Const correctness for toxcore/assoc.c
Const correctness in toxcore/onion_client.c
Const correctness in toxcore/friend_requests.c
Const correctness in toxcore/group_chats.c
Const correctness for various packet callbacks
Merge branch 'const_correctness' of https://github.com/schuetzm/ProjectTox-Core into schuetzm-const_correctness
Astyled code.
Fixed some warnings.