Update copyright year

Reviewed-by: Richard Levitte <levitte@openssl.org>

apps/errstr.c

diff --git a/apps/errstr.c b/apps/errstr.c
index af33a68..3ef01f0 100644
--- a/apps/errstr.c
+++ b/apps/errstr.c
@@ -1,5 +1,5 @@
 /*
- * Copyright 1995-2017 The OpenSSL Project Authors. All Rights Reserved.
+ * Copyright 1995-2018 The OpenSSL Project Authors. All Rights Reserved.
  *
  * Licensed under the OpenSSL license (the "License").  You may not use
  * this file except in compliance with the License.  You can obtain a copy