title: QWinTaskbarProgress won't show
body: <p>I'm using windows7 and Qt5.3.0
  I added below to my MainWindow's constructor but nothing shows on my taskbar. Did I miss something?</p>
  
  <pre><code>QWinTaskbarProgress * pTaskbarProgress = new QWinTaskbarProgress(this);
  pTaskbarProgress-&gt;setMinimum(0);
  pTaskbarProgress-&gt;setMaximum(100);
  pTaskbarProgress-&gt;setValue(50);
  pTaskbarProgress-&gt;show();
  </code></pre>