title: delete all QSpacerItem from a layout
body: <p>I've added a <code>QSpacerItem</code> to a layout using its <code>addStretch()</code> method.</p>
  
  <pre><code>layout-&gt;addStretch(1);
  </code></pre>
  
  <p>now i'd like to delete it but i didn't have any reference to it.</p>
  
  <p>how can I browse all <code>QLayoutItem</code> and only delete <code>QSpacerItem</code> ?</p>