when creating a DOCTYPE use "html" lowercase by default instead of "HTML"

* HTMLparser.c: when creating a DOCTYPE use "html" lowercase
  by default instead of "HTML"
* parser.c xmlreader.c: optimization, gain a few % parsing speed by
  avoiding calls to "areBlanks" when not needed.
* include/libxml/parser.h include/libxml/tree.h: some structure
  extensions for future work on using per-document dictionaries.
Daniel
diff --git a/HTMLparser.c b/HTMLparser.c
index 7c40474..90e2460 100644
--- a/HTMLparser.c
+++ b/HTMLparser.c
@@ -2137,7 +2137,7 @@
     cur->_private = NULL;
     if ((ExternalID != NULL) ||
 	(URI != NULL))
-	xmlCreateIntSubset(cur, BAD_CAST "HTML", ExternalID, URI);
+	xmlCreateIntSubset(cur, BAD_CAST "html", ExternalID, URI);
     return(cur);
 }
 
@@ -4002,7 +4002,7 @@
 	dtd = xmlGetIntSubset(ctxt->myDoc);
 	if (dtd == NULL)
 	    ctxt->myDoc->intSubset = 
-		xmlCreateIntSubset(ctxt->myDoc, BAD_CAST "HTML", 
+		xmlCreateIntSubset(ctxt->myDoc, BAD_CAST "html", 
 		    BAD_CAST "-//W3C//DTD HTML 4.0 Transitional//EN",
 		    BAD_CAST "http://www.w3.org/TR/REC-html40/loose.dtd");
     }
@@ -5058,7 +5058,7 @@
 	dtd = xmlGetIntSubset(ctxt->myDoc);
 	if (dtd == NULL)
 	    ctxt->myDoc->intSubset = 
-		xmlCreateIntSubset(ctxt->myDoc, BAD_CAST "HTML", 
+		xmlCreateIntSubset(ctxt->myDoc, BAD_CAST "html", 
 		    BAD_CAST "-//W3C//DTD HTML 4.0 Transitional//EN",
 		    BAD_CAST "http://www.w3.org/TR/REC-html40/loose.dtd");
     }