* getdate.y: Rewrite to use mktime.
<sys/timeb.h>: Don't include.
(mktime): Declare.
(struct timeb, timezone, DOOMSDAY, SECSPERDAY, DSTMODE, yyDSTmode,
ToSeconds, Convert, DSTcorrect, RelativeDate, RelativeMonth): Remove.
(ToHour): New function (part of the old ToSeconds fn).
(ToYear): New function (part of the old Convert fn).
(TABLE.value, yyDayOrdinal, yyDayNumber, yyTimezone, yyDay, yyHour,
yyMinutes, yyMonth, yySeconds, yyYear, yyRelMonth, yyRelSeconds,
Number): Now int instead of time_t.
(HOUR): Don't cast to time_t.
(tDAY_UNIT, tHOUR_UNIT, tYEAR_UNIT): New %tokens.
(UnitsTable): Use new units that are closer to the keywords.
(yyRelDay, yyRelHour, yyRelMinutes, yyRelYear): New variables.
(rel, relunit, get_date): Add support for them.
(time): Fix timezone calculations for negative half-hour offsets
when integer division truncates towards minus infinity.
(zone): Incorporiate DST calculation directly.
(get_date): 2nd arg is now time_t *, not struct timeb *.
Use mktime to do most of the work, instead of computing it ourselves.
Guard against falsely reporting errors near the time_t boundaries
when parsing times in other time zones.
Jim Meyering
6e5149f0ab