fixed the last core RelaxNG bug known #107083, shemas datatype ID/IDREF

* relaxng.c: fixed the last core RelaxNG bug known #107083,
  shemas datatype ID/IDREF support still missing though.
* xmlreader.c: fix a crashing bug with prefix raised by
  Merijn Broeren
* test/relaxng/testsuite.xml: augmented the testsuite with
  complex inheritance tests
Daniel
diff --git a/xmlreader.c b/xmlreader.c
index 8764e95..9d93f81 100644
--- a/xmlreader.c
+++ b/xmlreader.c
@@ -1865,7 +1865,7 @@
     if ((node->type != XML_ELEMENT_NODE) &&
 	(node->type != XML_ATTRIBUTE_NODE))
 	return(NULL);
-    if ((node->ns != NULL) || (node->ns->prefix != NULL))
+    if ((node->ns != NULL) && (node->ns->prefix != NULL))
 	return(xmlStrdup(node->ns->prefix));
     return(NULL);
 }