ticketcalendar: use `weekend_start` and `weekend_end` of `Locale` if Babel is available
ticketcalendar: use `weekend_start` and `weekend_end` of `Locale` if Babel is available


git-svn-id: 3a66edd98ef1b0c35353370f43e96c687f2de108@13261 7322e99d-02ea-0310-aa39-e9a107903beb

KKBOX/trac-ticket-calendar-plugin,KKBOX/trac-ticket-calendar-plugin