MString streaming work.

testing/mstring_test.cpp

@@ -79,6 +79,9 @@ int main(int argc, char **argv) {
    test22 << test23;
    std::cout << "mstring << string: [" << test22 <<  "]" << std::endl;
 
+//   coreutils::MString test24 = std::endl;
+//   std::cout << "mstring << endl: " << test24 << std::endl;
+   
    return 0;
 }