s to handle additional mouse-over signals
  from <tt>TGLViewer</tt>.</li>

<li><tt>TEveElement</tt> - Add 3 new functions:<pre>
    virtual TString  GetHighlightTooltip();
    virtual void     UnSelected();
    virtual void     UnHighlighted();
</pre></li>

<li><tt>TEveDigitSet</tt>, <tt>TEveQuadSet</tt>, <tt>TEveBoxSet</tt>
<ul>
  <li>Sub-class <tt>TEveDigitSet</tt> from <tt>TEveSecondarySelectable</tt>.</li>
  <li>Implement functions needed for internal selection.</li>
  <li>Add common base-class <tt>TEve