fix gcc warnings

Max Kellermann <max@duempel.org>
diff --git a/extensions/libip6t_dst.c b/extensions/libip6t_dst.c
index 4b4dcf9..9e4d870 100644
--- a/extensions/libip6t_dst.c
+++ b/extensions/libip6t_dst.c
@@ -26,7 +26,7 @@
 	{ .name = "dst-len",        .has_arg = 1, .val = '1' },
 	{ .name = "dst-opts",       .has_arg = 1, .val = '2' },
 	{ .name = "dst-not-strict", .has_arg = 1, .val = '3' },
-	{ }
+	{ .name = NULL }
 };
 
 static u_int32_t
@@ -168,7 +168,7 @@
 }
 
 static void
-print_options(int optsnr, u_int16_t *optsp)
+print_options(unsigned optsnr, u_int16_t *optsp)
 {
 	unsigned int i;