Fix sparse warnings: non-ANSI function declarations, 0 used as pointer
diff --git a/extensions/libip6t_ipv6header.c b/extensions/libip6t_ipv6header.c
index 3d21f45..04749e6 100644
--- a/extensions/libip6t_ipv6header.c
+++ b/extensions/libip6t_ipv6header.c
@@ -149,9 +149,9 @@
 }
 
 static const struct option opts[] = {
-	{ "header", 1, 0, '1' },
-	{ "soft", 0, 0, '2' },
-	{ 0 }
+	{ "header", 1, NULL, '1' },
+	{ "soft", 0, NULL, '2' },
+	{ }
 };
 
 static void