Fix sparse warnings: non-ANSI function declarations, 0 used as pointer
diff --git a/extensions/libipt_icmp.c b/extensions/libipt_icmp.c
index 9ee1baa..5be4f21 100644
--- a/extensions/libipt_icmp.c
+++ b/extensions/libipt_icmp.c
@@ -77,7 +77,7 @@
 };
 
 static void
-print_icmptypes()
+print_icmptypes(void)
 {
 	unsigned int i;
 	printf("Valid ICMP Types:");
@@ -110,8 +110,8 @@
 }
 
 static const struct option opts[] = {
-	{ "icmp-type", 1, 0, '1' },
-	{0}
+	{ "icmp-type", 1, NULL, '1' },
+	{ }
 };
 
 static void