Working on variables implementation:

- libxslt/transform.c libxslt/variables.[ch] libxslt/xslt.c
  libxslt/xsltInternals.h libxslt/xsltutils.h: changed a few
  structure to add an execution stack with variables. Tree
  valued variables still missing.
- TODO: updated
Daniel

libxslt/xslt.c

@@ -162,7 +162,6 @@ xsltFreeStylesheet(xsltStylesheetPtr sheet) {
 	return;
 
     xsltFreeTemplateHashes(sheet);
-    xsltFreeVariableHashes(sheet);
     xsltFreeTemplateList(sheet->templates);
     if (sheet->doc != NULL)
 	xmlFreeDoc(sheet->doc);