Chrono: Added format function to get the formatter of a reporter

[SVN r74622]

include/boost/chrono/stopwatches/reporters/stopwatch_reporter.hpp

@@ -79,11 +79,17 @@ namespace boost
         formatter_(*this, ec);
         reported_ = true;
       }
+
       bool reported() const
       {
         return reported_;
       }
 
+      formatter_type& format()
+      {
+        return formatter_;
+      }
+
     protected:
       formatter_type formatter_;
       bool reported_;