Add copyright notice.

Add copyright notice.

(number): Handle `Nov 11 1996' example; see Risks Digest 20.55
http://catless.ncl.ac.uk/Risks/20.55.html#subj18
(1999-08-27)

(<stdio.h>): Include only if testing.
(ISUPPER): Remove.
(ISLOWER, PC): New macros.
(<string.h>): Include if HAVE_STRING_H, not USG.
(bcopy): Remove.
(yymaxdepth, ..., yycheck): Don't bother to redefine, since we assume
bison.
(EPOCH_YEAR): Renamed from EPOCH.
(table): Renamed from TABLE.
(meridian): Now an anonymous enum.
(struct parser_control): New type.
(YYLEX_PARAM, YYPARSE_PARAM, YYSTYPE): New macros.
(yyInput, ..., yyRelYear): Migrated into struct parser_control.
(%pure_parser): Added, so that the parser is pure.
(%union): Removed; the type is now just plain int.
All %type directives removed.
(tLOCAL_ZONE): New %token.
(month_day_table): Renamed from MonthDayTable.
(gmtime, localtime, mktime, time): Declare only if not defined.
(meridian_table): New table.
(dst_table): New table.
(units_table): renamed from UnitsTable.
(relative_time_table): Renamed from OtherTable.
(time_zone_table): Renamed from TimezoneTable.  Modernized data.
(military_table): Renamed from MilitaryTable.
(to_hour): Renamed from ToHour.
(to_year): Renamed from ToYear.
(lookup_zone): New function.
(LookupWord): Renamed from lookup_word.
Use lookup_zone for time zones.
(yylex): Now reentrant.  All callers changed.
(get_date): Add support for local time zone abbreviations.
Make it reentrant.