Update the license end year

Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5121)

LICENSE

@@ -10,7 +10,7 @@
   ---------------
 
 /* ====================================================================
- * Copyright (c) 1998-2017 The OpenSSL Project.  All rights reserved.
+ * Copyright (c) 1998-2018 The OpenSSL Project.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions