Fix sparse warnings: non-ANSI function declarations, 0 used as pointer
diff --git a/extensions/libxt_length.c b/extensions/libxt_length.c
index 79e6f41..5353d2c 100644
--- a/extensions/libxt_length.c
+++ b/extensions/libxt_length.c
@@ -21,8 +21,8 @@
 }
   
 static const struct option opts[] = {
-	{ "length", 1, 0, '1' },
-	{0}
+	{ "length", 1, NULL, '1' },
+	{ }
 };
 
 static u_int16_t