iproute: make ss --help output to stdout

Peter Palfrader said in http://bugs.debian.org/545008 that
"--help output, if explicitly requested, should go to stdout, not stderr."
which this patch fixes.

Additionally, the exit code was adjusted to success if help was
explicitly requested.

(Syntax error still outputs to stderr and has the same exit code.)
Signed-off-by: Andreas Henriksson <andreas@fatal.se>

misc/ss.c

@@ -2331,12 +2331,9 @@ int print_summary(void)
 	return 0;
 }
 
-
-static void usage(void) __attribute__((noreturn));
-
-static void usage(void)
+static void _usage(FILE *dest)
 {
-	fprintf(stderr,
+	fprintf(dest,
 "Usage: ss [ OPTIONS ]\n"
 "       ss [ OPTIONS ] [ FILTER ]\n"
 "   -h, --help		this message\n"
@@ -2368,6 +2365,19 @@ static void usage(void)
 "   -F, --filter=FILE   read filter information from FILE\n"
 "       FILTER := [ state TCP-STATE ] [ EXPRESSION ]\n"
 		);
+}
+
+static void help(void) __attribute__((noreturn));
+static void help(void)
+{
+	_usage(stdout);
+	exit(0);
+}
+
+static void usage(void) __attribute__((noreturn));
+static void usage(void)
+{
+	_usage(stderr);
 	exit(-1);
 }
 
@@ -2514,7 +2524,7 @@ int main(int argc, char *argv[])
 			else if (strcmp(optarg, "netlink") == 0)
 				preferred_family = AF_NETLINK;
 			else if (strcmp(optarg, "help") == 0)
-				usage();
+				help();
 			else {
 				fprintf(stderr, "ss: \"%s\" is invalid family\n", optarg);
 				usage();
@@ -2596,6 +2606,7 @@ int main(int argc, char *argv[])
 			exit(0);
 		case 'h':
 		case '?':
+			help();
 		default:
 			usage();
 		}