[css2] added value of none to quotes prop

--HG--
extra : convert_revision : svn%3A73dc7c4b-06e6-40f3-b4f7-9ed1dbc14bfc/trunk%40945

Author: ianbjacobs

css2/properties/properties.db

@@ -352,7 +352,7 @@ no;; N/A;; visual */
 /* content;; [ <string> | <uri> | <counter> | open-quote | close-quote | no-open-quote | no-close-quote ]+ | inherit;; empty string;;
 :before and :after;; no;; N/A;; all */
 
-/* quotes;; [<string> <string>]* | inherit;; depends on user agent;;
+/* quotes;; [<string> <string>]+ | none | inherit;; depends on user agent;;
 *;; yes;; N/A;; visual */
 
 /* counter-reset;; [ <identifier> <integer>? ]+ | inherit;; depends on user