Description:
------------
When I try to evaluate the namespace of an xpath node php crashes with a segmentation fault.

Reproduce code:
---------------
<?php
$s = '<?xml version="1.0" ?>';
$s .= '<test:foo xmlns:test="http://www.umweltdatenkatalog.de/udk">';
$s .= '<test:bar>abc';
$s .= '</test:bar>';
$s .= '</test:foo>';

$doc = domxml_open_mem($s);
$ctx_p = xpath_new_context($doc);
$namesp = xpath_eval($ctx_p, '//namespace::*');
echo '<pre><br/>';
print_r($doc);
print_r($ctx_p);
print_r($namesp);
echo '</pre>';
?>

Expected result:
----------------
The expected result is an Xpath-Object with
the name "xmlns:namespace-prefix" and the value "namespace-uri". In the example that would be:

name=xmlns:test
value=http://www.umweltdatenkatalog.de/udk

Actual result:
--------------
The php-interpreter causes an programm error and is closed.