title: JLayeredPane z-order issue
body: <p>While using JLayeredPane to add Compnents in z-order, I noticed some issue:</p>
  
  <pre><code>JLayeredPane lp = getLayeredPane();
  
  JButton top = new JButton(); ...
  JButton middle = new JButton(); ...
  JButton bottom = new JButton(); ...
  </code></pre>
  
  <p>Works bad:</p>
  
  <pre><code>lp.add(top,2);
  lp.add(middle,1);
  lp.add(bottom,3);
  </code></pre>
  
  <p>Works good:</p>
  
  <pre><code>lp.add(top,new Integer(2));
  lp.add(middle,new Integer(1));
  lp.add(bottom,new Integer(3));
  </code></pre>
  
  <p>Here you can see how it looks: <a href="http://i.imgur.com/eqH2El8.png" rel="nofollow">http://i.imgur.com/eqH2El8.png</a></p>
  
  <p>Why is literal constant not converted into Integer object, and it does not work properly?</p>