[tz] About Asia/Hanoi

[Paul Eggert]

Meno Hochschild wrote:
> Should there be a link between Asia/Hanoi and Asia/Ho_Chi_Minh in TZDB?
> ...
> (see: https://github.com/ThreeTen/threetenbp/issues/57)
Since the same problem was reported for Asia/Yekaterinburg, I don't see why it 
matters whether Asia/Hanoi is in backzone or in some other file. Anyway, we're 
not likely to create unnecessary names merely because of improperly configured 
or buggy software; otherwise we'd need entries for every misspelling of every 
city on the planet. Asia/Hanoi is in backzone because it is beyond the scope of 
the tz database: Hanoi's time history since 1970 is identical to that of 
Asia/Bangkok, the entry that zone1970.tab uses for North Vietnam.