*solar.el (solar-setup, solar-ephemeris-time, sunrise-sunset): Change

*solar.el (solar-setup, solar-ephemeris-time, sunrise-sunset): Change
        Universal Time (UT) to Coordinated Universal Time (UTC).
        (solar-time-string): Use calendar-daylight-time-offset instead of
        1 hr, and use calendar-daylight-savings-switchover-time instead of
        midnight.  Add an optional parameter to allow forcing the use of
        standard or daylight savings time.  Fix code so it works in
        southern hemisphere (start of dst precedes end of dst in a
        calendar year) and when dst either starts or ends in a calendar
        year, but not both.