Description:
------------
When I use a XML file with DTD, the root node doesn't have any children (but xpath query works) and if I removed the DTD, the DOM seems ok

Reproduce code:
---------------
function test( $filename ) { 
  $xml = new DOMDocument();
  $xml->load( $filename, LIBXML_NOBLANKS );

  echo "\n$filename\n";
  echo "Root of XML : " . $xml->firstChild->nodeName . "\n";
  echo "First child of XML Root : " . $xml->firstChild->firstChild->nodeName . "\n";

  $xpath = new DOMXpath( $xml );

  echo "result of /mame/game xpath query : \n";
  $r = $xpath->query("/mame/game");
  for( $i=0; $i<$r->length; $i++ ) { 
    echo $r->item($i)->nodeName . "\n";
  }

}
test( "file_without_dtd.xml" );
test( "file_with_dtd.xml" );



Expected result:
----------------
with the two XML files: 
file_without_dtd.xml
Root of XML : mame
First child of XML Root : game
result of /mame/game xpath query : 
game

file_with_dtd.xml
Root of XML : mame
First child of XML Root : game
result of /mame/game xpath query : 
game


Actual result:
--------------
file_without_dtd.xml
Root of XML : mame
First child of XML Root : game
result of /mame/game xpath query : 
game

file_with_dtd.xml
Root of XML : mame
First child of XML Root : 
result of /mame/game xpath query : 
game