Adding nsExtensibleStringBundle support.

intl/strres/public/nsIStringBundle.idl

@@ -49,5 +49,6 @@ interface nsIStringBundle : nsISupports
 interface nsIStringBundleService : nsISupports
 {
    nsIStringBundle CreateBundle([const] in string aURLSpec, in nsILocale aLocale);
+   nsIStringBundle CreateExtensibleBundle([const] in string aRegistryKey, in nsILocale aLocale);
    nsIStringBundle CreateXPCBundle([const] in string aURLSpec, [const] in wstring aLocaleName);
 };