#1 add ^C signal handler

[Brad H]

Add a signal handler to catch, among others, ^C. which
i think is SIGINT.
upon catching this signal, wc1 should:

1. send CMD_BYE to all connected clients
2. close all client sockets
3. close listener socket
4. gracefully shutdown the cam device
5. do any syslogging if necessary
6. print informative message explaining sig caught.
7. ?