this also obsoletes ListenIPv4 and ListenIPv6 options.
If Listen is unset, it is treated as Listen="::,0.0.0.0".
Note: ListenIPv4 and ListenIPv6 options are still recognized,
but ngircd will print a warning if they are used in the config file.
Also, some plattforms require that ai_socktype
is set in the getaddrinfo() hints structure.