Stats and other improvements.

 * Sender prints send stats.
 * -c the stats interval in both client and server. -C for max send
   in client.
 * Sink reports negative delta incidents in its stats.
 * Remove useless fclose(stdin)/setsid() daemonization; C-c goes to the
   foreground process group, so want to stay in that to catch said C-c.
Include out-of-order counts in final summary.
Write man pages.