Add copyright comments to the hash documentation source.

[SVN r35288]

doc/ref.xml

@@ -1,3 +1,10 @@
+
+<!--
+Copyright Daniel James 2005-2006
+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)
+-->
+
 <library-reference>
   <section id="hash.reference.specification">
     <para>For the full specification, see section 6.3 of the