nsIStringBundleService in Firefox 3.5

 flushes the string bundle cache - useful when the locale changes or
 when we need to get some extra memory back
 
 at some point, we might want to make this flush all the bundles,
 because any bundles that are floating around when the locale changes
 will suddenly contain bad data

 Formats a message string from a status code and status arguments.
 @param aStatus - The status code. This is mapped into a string ID and
            and used in the string lookup process (see nsIErrorService).
 @param aStatusArg - The status message argument(s). Multiple arguments
            can be separated by newline ('
') characters.
 @return the formatted message