Support SO_PEERCRED

[alexanderkjeldaas]

I'd like the daemon to be able to use the native credentials passing mechanism on Linux, namely SO_PEERCRED or SO_PASSCRED

http://linux.die.net/man/7/socket

http://hackage.haskell.org/package/network-2.0/docs/Network-Socket.html#v%3AgetPeerCred

[alexanderkjeldaas]

This also requires supporting unix domain sockets. So supporting something like

data DaemonOptions = {
      daemonBind :: [N.SockAddr]
   ,  daemonPidFile :: PidFile
   , printOnDaemonStarted :: Bool
}

would make it possible to specify whether to bind to IPv4, IPv6 and/or unix domain sockets.