privoxy: Allow multiple listen-address options (#444719)

        freeformType = configType;

        options.listen-address = mkOption {

          type = types.str;

          type = types.either types.str (types.listOf types.str);

          default = "127.0.0.1:8118";

          description = "Pair of address:port the proxy server is listening to.";

        };