message: Bug fix on Windows due to a missing &
diff: @@ -57,7 +57,7 @@ namespace {
  };
  template< typename U, typename T >
  - static const T& mapped_value( const std::map< U, T > map, const U& key )
  + static const T& mapped_value( const std::map< U, T >& map, const U& key )
  {
  return map.find( key )->second;
  }
  