Add missing include in s2n_certificate.c
string.h is needed for strnlen.
/*
- * Copyright 2014 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License").
* You may not use this file except in compliance with the License.
#include <s2n.h>
#include <openssl/x509v3.h>
#include <openssl/pem.h>
+#include <string.h>
#include <strings.h>
#include "crypto/s2n_certificate.h"
