Description:
------------
When using DOM to create a new <xsl:include> and insert it in the xslt document php comes up with a error as seen below.

Reproduce code:
---------------
<?php
$xsl = new DOMDocument('1.0', 'UTF-8');
$test = <<<EOF
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" 
				xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
	<xsl:output method="html" indent="yes"/>
	<xsl:template match="/">
		<xsl:apply-templates/>
	</xsl:template>
</xsl:stylesheet>
EOF;
$xsl->loadXML($test);

$import = $xsl->createElement('xsl:import');
$import->setAttribute('href', 'login.xsl');

$xsl->documentElement->insertBefore($import, $xsl->documentElement->firstChild);

echo $xsl->saveXML();

$html = new XSLTProcessor();
$html->importStylesheet($xsl);
?>

Expected result:
----------------
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0"><xsl:import href="login.xsl"/>
	<xsl:output method="html" indent="yes"/>
	<xsl:template match="/">
		<xsl:apply-templates/>
	</xsl:template>
</xsl:stylesheet>
<br />
<b>Warning</b>:  Found a top-level element xsl:import with null namespace URI in <b>D:\steffen\frontend\test.php</b> on line <b>23</b><br />

Actual result:
--------------
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0"><xsl:import href="login.xsl"/>
	<xsl:output method="html" indent="yes"/>
	<xsl:template match="/">
		<xsl:apply-templates/>
	</xsl:template>
</xsl:stylesheet>