Communication handling and ping

I added main_loop based communication handling to both, KIRO server and client.
A few race conditions and deadlocks needed to be fixed, but its working now.
Also, i added a kiro_client_ping_server function and changed the latency test accordingly.
@matze: You have a keen eye for bad GLib usage. If you have some time, can you maybe check if i have made any larger mistakes? Thanks!