Sync DOMImplementation.createDocument() IDL with spec

LayoutTests/fast/dom/DOMImplementation/detached-doctype.html

 <p>Test for <a href="https://bugs.webkit.org/show_bug.cgi?id=26402">bug 26402<a/>: Crashes when using a detached DocumentType node.</p>
 <p>PASS if no crash.</p>
 <SCRIPT>
 function gc()
 {
     if (window.GCController)
         return GCController.collect();
 
     for (var i = 0; i < 10000; i++)
         var s = new String("");
 }
 
 if (window.testRunner)
     testRunner.dumpAsText();
 
 var o = document.implementation.createDocumentType('x', null, null);
-var doc = document.implementation.createDocument("doc", null, 0);
+var doc = document.implementation.createDocument("doc", null);
 for (i in o) {
     try { o[i]; } catch (e) {}
     try { o[i](); } catch (e) {}
 }
 o.addEventListener("click", function() {}, true);
 o.removeEventListener("click", function() {}, true);
 o.childNodes;
 o.childNodes.item(0);
 o.firstChild;
 gc();
 document.write("DONE");
 </SCRIPT>