don't insert string type

[GoogleCodeExporter]

As below is error:
test_case(tree_any_type) 
{
  tree<string> tr;
  tr.insert(tr.end(),"1");
}

test_runner.cpp:130:25: error: call of overloaded 
‘insert(the::_tree_private::mutable_tr<std::basic_string<char>, 
the::tree<std::basic_string<char> > >::pre_iterator, const char [2])’ is 
ambiguous
   tr.insert(tr.end(),"1");

As below is right:
test_case(tree_any_type) 
{
  tree<string> tr;
  tr.insert(tr.end(),string("1")); 
}

Original issue reported on code.google.com by [email protected] on 17 Jul 2013 at 3:26