GitLab

* SIGINT is now being handled
* the peers can connect to each other now

* neighbours, peers and linked list functions in alphabetical order
* more functions in the linked list
* the peers are being represented by their own structure
* linkedlist of pending_neighbours and peers for the next commit

Few renames (nothing set to stone---still trying to find the best fit)
IPv6-only code (let's ditch IPv4! \o/ )
Conversion an IP address to string representation by a separate function

Overall: no functionality change

Autotools
coincerd (daemon) with TODOs
coincer (client for interacting with daemon)