added support and APIs needed for the catalog PI cleanup Daniel

* include/libxml/catalog.h include/libxml/parser.h
  include/libxml/xmlerror.h catalog.c parser.c parserInternals.c
  xmlIO.c: added support and APIs needed for the catalog PI
* include/libxml/xmlIO.h: cleanup
Daniel
diff --git a/include/libxml/parser.h b/include/libxml/parser.h
index de0bebb..1cf7f52 100644
--- a/include/libxml/parser.h
+++ b/include/libxml/parser.h
@@ -217,6 +217,7 @@
 
     int                loadsubset;    /* should the external subset be loaded */
     int                linenumbers;   /* set line number in element content */
+    void              *catalogs;       /* document's own catalog */
 };
 
 /**