fixing #61290 "namespace nodes have no parent" long standing divergence

* xpath.c: fixing #61290 "namespace nodes have no parent"
  long standing divergence from the XPath REC. NodeSets
  simply hold a copy of namespace nodes and those node ->next
  points to the parent (which may not be the node carrying the
  definition).
* include/libxml/xpath.h: flagged but didn't added a possible
  speedup
* DOCBparser.c HTMLparser.c: removed some warnings from push
  parser due to new state being added.
* tree.c: new fix from Boris Erdmann
* configure.in c14n.c include/libxml/c14n.h testC14N.c: added
  the XML Canonalization support from Aleksey Sanin
Daniel

include/libxml/xpath.h

@@ -62,6 +62,7 @@ struct _xmlNodeSet {
     int nodeNr;			/* number of nodes in the set */
     int nodeMax;		/* size of the array as allocated */
     xmlNodePtr *nodeTab;	/* array of nodes in no particular order */
+    /* @@ with_ns to check wether namespace nodes should be looked at @@ */
 };
 
 /*