added unbound to external deps

external/unbound/compat/explicit_bzero.c

@@ -0,0 +1,22 @@
+/*	$OpenBSD: explicit_bzero.c,v 1.3 2014/06/21 02:34:26 matthew Exp $ */
+/*
+ * Public domain.
+ * Written by Matthew Dempsky.
+ */
+#include "config.h"
+#include <string.h>
+
+__attribute__((weak)) void
+__explicit_bzero_hook(void *ATTR_UNUSED(buf), size_t ATTR_UNUSED(len))
+{
+}
+
+void
+explicit_bzero(void *buf, size_t len)
+{
+#ifdef UB_ON_WINDOWS
+	SecureZeroMemory(buf, len);
+#endif
+	memset(buf, 0, len);
+	__explicit_bzero_hook(buf, len);
+}