Update copyright line to 2015
diff --git a/programs/util/strerror.c b/programs/util/strerror.c
index e6962df..e4d8d4a 100644
--- a/programs/util/strerror.c
+++ b/programs/util/strerror.c
@@ -1,7 +1,7 @@
 /*
  *  Translate error code to error string
  *
- *  Copyright (C) 2006-2012, ARM Limited, All Rights Reserved
+ *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
  *
  *  This file is part of mbed TLS (https://polarssl.org)
  *