Big XPath cleanup continues, one URI fix:

- xpath.[ch] debugXML.c testXPath.c: fixed the XPath evaluation
  engine, should be far more stable, incorporated a new version of
  preceding/following axis, need testing
- uri.c: fixed file:///c:/a/b/c problem
- test/XPath/tests/idsimple: augmented the XPath tests
Daniel

include/libxml/xpath.h

@@ -143,7 +143,6 @@ struct _xmlXPathAxis {
 struct _xmlXPathContext {
     xmlDocPtr doc;			/* The current document */
     xmlNodePtr node;			/* The current node */
-    xmlNodeSetPtr nodelist;		/* The current node list */
 
     int nb_variables;			/* number of defined variables */
     int max_variables;			/* max number of variables */