More cleanups, XSLT induced, start looking okay:

- xpath.[ch]: still a lot of cleanup based on XSLT, added
  xmlXPathConvert{String,Number,Boolean} to be able to make
  type casts without a context stack, fixed some implementation
  problems related to the absence of context at parse-time,
  added xmlXPathEvalPredicate() and xmlXPathFreeCompExpr()
  in the public API too
- xpointer.c xpathInternals.h: we need to know at parse time
  whether we are compiling an XPointer
Daniel

xpointer.c

@@ -1292,6 +1292,7 @@ xmlXPtrEval(const xmlChar *str, xmlXPathContextPtr ctx) {
 	return(NULL);
 
     ctxt = xmlXPathNewParserContext(str, ctx);
+    ctxt->xptr = 1;
     xmlXPtrEvalXPointer(ctxt);
 
     if ((ctxt->value != NULL) &&