* solar.el (calendar-holiday-solar-equinoxes-solstices): Renamed

* solar.el (calendar-holiday-solar-equinoxes-solstices): Renamed
        solar-equinoxes-solstices.
        (calendar-time-display-form, calendar-latitude,
        calendar-longitude): Moved from calendar.el.
        (calendar-time-zone, calendar-standard-time-zone-name,
        calendar-daylight-time-zone-name,
        calendar-daylight-savings-starts, calendar-daylight-savings-ends):
        Take default values from calendar-current-time-zone, instead of
        being overwritten in open code if they were set to nil.
        (solar-time-string): Subtract calendar-daylight-time-offset when
        computing dst-ends.  Avoid rounding errors when rounding time to
        the nearest minute.