Update copyright line to 2015
diff --git a/library/xtea.c b/library/xtea.c
index 5d78df8..84dc025 100644
--- a/library/xtea.c
+++ b/library/xtea.c
@@ -1,7 +1,7 @@
 /*
  *  An 32-bit implementation of the XTEA algorithm
  *
- *  Copyright (C) 2006-2013, ARM Limited, All Rights Reserved
+ *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
  *
  *  This file is part of mbed TLS (https://polarssl.org)
  *