Description:
------------
libxml 2.6.31

When importing previously removed element into the new document the namespaceURI is not preserved.

It is preserved only if the @xmlns declaration attribute is present on the element itself. Does not work if it was declared on former ancestor.

Reproduce code:
---------------
$rcpt=new DOMDocument; $rcpt->loadXML("<rcpt></rcpt>");
// XMLNS on parent
$dnr1=new DOMDocument; $dnr1->loadXML("<dnr xmlns:sys='http://www.1stomni.com/spire'><sys:donate/></dnr>");
// XMLNS on element
$dnr2=new DOMDocument; $dnr2->loadXML("<dnr><sys:donate xmlns:sys='http://www.1stomni.com/spire'/></dnr>");

getGift($rcpt, $dnr1->documentElement->removeChild($dnr1->documentElement->firstChild));
getGift($rcpt, $dnr2->documentElement->removeChild($dnr2->documentElement->firstChild));

function getGift($dom, $gift) {
	echo "before: \"$gift->namespaceURI\"; after: \"".$dom->documentElement->appendChild($dom->importNode($gift))->namespaceURI."\"\n";
}


Expected result:
----------------
before: "http://www.1stomni.com/spire"; after: "http://www.1stomni.com/spire"
before: "http://www.1stomni.com/spire"; after: "http://www.1stomni.com/spire"


Actual result:
--------------
before: "http://www.1stomni.com/spire"; after: ""
before: "http://www.1stomni.com/spire"; after: "http://www.1stomni.com/spire"