title: multiple "using namespace" in a line?
body: <p>I searched but I could not find related question.
  Please correct me if I'm wrong.</p>
  
  <p>In my project I use the following:</p>
  
  <pre><code>using namespace std;
  using namespace sf;
  </code></pre>
  
  <p>I want it to be like below.</p>
  
  <pre><code>using namespace std, sf;
  </code></pre>
  
  <p>Thanks in advance!</p>