add or update See www.boost.org comments

[SVN r16708]

include/boost/visit_each.hpp

@@ -11,7 +11,7 @@
 // This software is provided "as is" without express or implied warranty,
 // and with no claim as to its suitability for any purpose.
  
-// For more information, see http://www.boost.org
+// For more information, see http://www.boost.org/libs/signals
 
 #ifndef BOOST_VISIT_EACH_HPP
 #define BOOST_VISIT_EACH_HPP