report_errors with expected failures (#51)

* Return number of failures from report_errors

include/boost/core/lightweight_test.hpp

@@ -383,14 +383,13 @@ inline int report_errors()
     {
         BOOST_LIGHTWEIGHT_TEST_OSTREAM
           << "No errors detected." << std::endl;
-        return 0;
     }
     else
     {
         BOOST_LIGHTWEIGHT_TEST_OSTREAM
           << errors << " error" << (errors == 1? "": "s") << " detected." << std::endl;
-        return 1;
     }
+    return errors;
 }
 
 } // namespace boost