title: QFileDialog::getSaveFileName and default selectedFilter
body: <p>I have getSaveFileName with some filters and I want one of them to be selected when user opens the "Save" dialog. Qt documentation says the following:</p>
  
  <blockquote>
    <p>The default filter can be chosen by setting selectedFilter to the desired value.</p>
  </blockquote>
  
  <p>I try the following variant:
  </p>
  
  <pre><code>QString selFilter="All files (*.*)";
  QFileDialog::getSaveFileName(this,"Save file",QDir::currentPath(),
      "Text files (*.txt);;All files (*.*)",&amp;selFilter);
  </code></pre>
  
  <p>But when the dialog appears, the "Text files" filter (in general case, the first filter from the list) is selected. I also tried all of the following:</p>
  
  <pre class="lang-cpp prettyprint-override"><code>selFilter="All files";
  selFilter="All files (*.*)\n";
  selFilter="All files (*.*);;";
  selFilter="All files (*.*)\0";
  </code></pre>
  
  <p>and different mixtures of this variants. The format of the filter list in my code is done according to the documentation (example line from Qt docs):
  </p>
  
  <pre><code>"Images (*.png *.xpm *.jpg);;Text files (*.txt);;XML files (*.xml)"
  </code></pre>
  
  <p>Note that output to selFilter variable works properly: after user press OK, selFilter variable contains the filter selected by the user.</p>
  
  <p>Platform: Linux(OpenSUSE 12.1), Qt 4.7.4, gcc 4.6.2.</p>
  
  <p>So how to set up the default filter?!</p>