POC: implement TCP server on C

We need a POC of the TCP server (simple C implementation) to test COIO. It should be a dynamic library with exported functions:

1. start TCP server, parameters (listen address, length of the clients' queue, client idle timeout)
   • non-blocking listening to a socket within a loop (server fiber)
   • accept new connections in a child fibers, write to log information about new connected client
   • disconnect connected clients after idle timeout, write to log a message about disconnection
2. stop TCP server

We also need a build readme and some simple connection tests that everything works.