fixing AIX tinderbox

re-checking this in.  New fix that jag and I worked out (ok HE did!)
r=jaggernaut@netscape.com

editor/libeditor/html/nsHTMLEditorStyle.cpp

@@ -1411,7 +1411,9 @@ nsHTMLEditor::RelativeFontChangeOnTextNode( PRInt32 aSizeChange,
     if (NS_FAILED(res)) return res;
   }
 
-  nsAutoString nodeType(aSizeChange==1 ? NS_LITERAL_STRING("big") : NS_LITERAL_STRING("small"));
+  NS_NAMED_LITERAL_STRING(bigSize, "big");
+  NS_NAMED_LITERAL_STRING(smallSize, "small");
+  const nsAString& nodeType = (aSizeChange==1) ? NS_STATIC_CAST(const nsAString&, bigSize) : NS_STATIC_CAST(const nsAString&, smallSize);
   // look for siblings that are correct type of node
   nsCOMPtr<nsIDOMNode> sibling;
   GetPriorHTMLSibling(node, address_of(sibling));