title: QUdpSocket bind for multicast with ShareAddress fails
body: <p>The simple code belows fails on Windows with QT5.2 when another process is already bound on the specified port. The ShareAddress flag should allow binding multiple times however. On MacOSX it works fine.</p>
  
  <pre><code>if (false == bind(QHostAddress::AnyIPv4, port_, QUdpSocket::ShareAddress))
  {
      qDebug() &lt;&lt; "Warn: cannot bind to the multicast port " &lt;&lt; port_;
      qDebug() &lt;&lt; error();
  }
  joinMulticastGroup(QHostAddress(address_));
  </code></pre>
  
  <p>Is it a bug in QT ? If so is there a workaround ?</p>
  
  <p>Thanks.</p>