Description:
------------
The LIBXML_XINCLUDE paramter given to the SimpleXML::__construct() is being ignored. 

Xinclude does work with DOMDocument.

Using php-5.2.3


Reproduce code:
---------------
<?php

$xml = '
<test>
 <xi:include href="xmltobeincluded.xml"
xmlns:xi="http://www.w3.org/2001/XInclude" />
</test>
';

$x = new SimpleXMLElement($xml, LIBXML_XINCLUDE);

echo $x->asXML();
?>

Expected result:
----------------
<test>
  <xtest>
   value
  </xtest>
</test>

Actual result:
--------------
<?xml version="1.0"?>
<test>
 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="xmltobeincluded.xml"/>
</test>