Description:
------------
The problem occurs when an element has an unused namespace node
xmlns:default which is hanging around, unused.

When imorting a node under certain conditions, the parent node sets an xmlns:default which is intended to apply to the imported Node, but doesn't because xmlns:default applies instead.

The net effect is that the imported node changes namespace.

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

$aDOM = new DOMDocument;
$aDOM->loadXML('<?xml version="1.0"?><f2f:a xmlns:f2f="http://friend2friend.net"/>');
$a= $aDOM->firstChild;
echo 'DOM is add into is '.$aDOM->saveXML().chr(13);
$ok = new DOMDocument;
$ok->loadXML('<f2f:ok xmlns:f2f="http://friend2friend.net" xmlns="REAL"><watch-me xmlns:default="BOGUS"/></f2f:ok>');
$imported= $aDOM->importNode($ok->firstChild, true);
echo 'Node to import is '.$aDOM->saveXML($imported).chr(13).chr(13);
$a->appendChild($imported);
echo 'Result is '.$aDOM->saveXML();

?>


Expected result:
----------------
DOM is add into is <?xml version="1.0"?>
<f2f:a xmlns:f2f="http://friend2friend.net"/>

Node to import is <f2f:ok xmlns:f2f="http://friend2friend.net" xmlns="REAL"><watch-me xmlns:default="BOGUS"/></f2f:ok>

Result is <?xml version="1.0"?>
<f2f:a xmlns:f2f="http://friend2friend.net"><f2f:ok xmlns:default1="REAL"><default1:watch-me xmlns:default="BOGUS"/></f2f:ok></f2f:a>


Actual result:
--------------
DOM is add into is <?xml version="1.0"?>
<f2f:a xmlns:f2f="http://friend2friend.net"/>

Node to import is <f2f:ok xmlns:f2f="http://friend2friend.net" xmlns="REAL"><watch-me xmlns:default="BOGUS"/></f2f:ok>

Result is <?xml version="1.0"?>
<f2f:a xmlns:f2f="http://friend2friend.net"><f2f:ok xmlns:default="REAL"><default:watch-me xmlns:default="BOGUS"/></f2f:ok></f2f:a>