Missing copyright messages

meta/explicit-failures-markup.xml

@@ -1,4 +1,10 @@
 <?xml version="1.0" encoding="utf-8"?>
+<!--
+ Copyright 2017-2018 Daniel James
+ Distributed under the Boost Software License, Version 1.0.
+ (See accompanying file LICENSE_1_0.txt or copy at
+ http://www.boost.org/LICENSE_1_0.txt)
+-->
 <explicit-failures-markup>
     <!-- unordered -->
     <library name="unordered">