New file time.tab, superseding zone.tab

It allows multiple country codes per zone.  Switch code and data to
use the new format, along with the recently-added Crozet Islands entry.
The old zone.tab file is still installed but is deprecated.
The new file uses UTF-8; add commentary saying that iso3166.tab is
planned to change to UTF-8.
* Theory, tzselect.8 (FILES): zone.tab -> time.tab.
* africa (Indian/Alfred_Faure): Remove link.
* antarctica: Mention Possession Island in comments.
* checktab.awk: Add support for checking time.tab.
* iso3166.tab: Mention planned switch to UTF-8.
Update ISO 3166-1 Newsletter from VI-15 to VI-16.
* time.tab: New file.
* tzselect.ksh (zonetabtype): New variable.
Add undocumented -t option, meant for developer testing.
(TZ_ZONE_TABLE): Use zonetabtype.
(output_distances, countries, regions, TZ): Support time.tab format.
(quoted_continents, distance_table, countries, regions)
(TZ, TZ_for_date): Quote shell strings more carefully.
* zone.tab: Refer to time.tab for detailed comments about format.
(Indian/Alfred_Faure): Remove.
* Makefile (TIMETABLES): New macro.
(TABDATA, install, check_tables): Use it.
(check_character_set, check_tables): Check time.tab too.
(check_time_t_alternatives): Use time.tab, not zone.tab.
* NEWS: Document the above.