fixed an uninitialized variable extended the API to add the parser,

* valid.c: fixed an uninitialized variable
* xmlregexp.c include/libxml/xmlregexp.h: extended the API to
  add the parser, serializer and some debugging
* include/libxml/xmlversion.h.in: made the new support compiled
  by default if Schemas is included
* testRegexp.c: cleanup and integration of the first part of the
  new code with a special switch
* xmllint.c: show up Expr in --version if compiled in
* include/libxml/tree.h: moved the xmlBuffer definition up
Daniel
diff --git a/valid.c b/valid.c
index a4a9b61..35c21ae 100644
--- a/valid.c
+++ b/valid.c
@@ -2716,7 +2716,7 @@
     } else if (elem == NULL) {
 	return(0);
     } else {
-	xmlAttributePtr attrDecl;
+	xmlAttributePtr attrDecl = NULL;
 
 	xmlChar felem[50], fattr[50];
 	xmlChar *fullelemname, *fullattrname;