Implemented support for custom to_string overloads for converting boost::error_info objects to string by the boost::diagnostic_information function.

[SVN r50507]

include/boost/exception/info.hpp

@@ -15,6 +15,14 @@
 namespace
 boost
     {
+    template <class Tag,class T>
+    inline
+    typename enable_if<has_to_string<T>,std::string>::type
+    to_string( error_info<Tag,T> const & x )
+        {
+        return to_string(x.value());
+        }
+
     template <class Tag,class T>
     inline
     error_info<Tag,T>::
@@ -45,7 +53,7 @@ boost
     error_info<Tag,T>::
     value_as_string() const
         {
-        return to_string_stub(value_);
+        return to_string_stub(*this);
         }
 
     namespace