title: operator suffix for std::string in c++14
body: <p>I install Clang 3.4, and test suffix operator for string literal ""s.</p>
  
  <pre><code>#include &lt;string&gt;
  
  //1. using namespace std; // without compile error.
  //2. using std::operator ""s; // or without it compile error, too.
  // for success compiles, need 1. or 2. line.
  
  int main()
  {
      auto s = "hello world"s; 
  }
  </code></pre>
  
  <p>If I comment 1 and 2 , I get compile error. But I know in big projects  1.-method is bad,
  and 2.-method is stranger.</p>
  
  <p>QA: Can I use operator ""s   without any writing <code>using namespace std</code> and <code>using std::operator ""s</code> ?  </p>