l XML data from the specified pull parser and return the
 resulting content tree.

 <p>
 This method is an <a href="#unmarshalGlobal">Unmarshal Global Root method</a>.

 <p>
 This method assumes that the parser is on a START_DOCUMENT or
 START_ELEMENT event.  Unmarshalling will be done from this 
 start event to the corresponding end event.  If this method 
 returns successfully, the <code>reader</code> will be pointing at 
 the token right after the end event.</div>
<dl>
<dt><span class="paramLabel">Parame