[tz] Add new timezone for Hanoi Capital, Vietnam

[Michael H Deckers]

   On 2019-02-17 18:02, KP wrote:
> These are the reasons that I think are reasonable
> - After merging with Ha Tay, Hanoi (capital) is the largest province in
> Vietnam
> - +7:00 (North Vietnam and All Vietnam since 1975) timezone has been the
> longest unified timezone ever, compared to Asia/Saigon, Asia/Ho_Chi_Minh
> (modified many times)




    What I find more disturbing is the following:

    The tzdb "time zone" Asia/Hanoi in backzone/ gives
    reliable historical detail before 1970. But tzdb data
    do not give any clue which "time zone" can be used for
    it when the historical detail is not needed, because
    there is no link from Asia/Hanoi to Asia/Bangkok.
    I would find such a link helpful, at least for the
    connaisseurs of historical timestamps.

    As far as I can see, this is the only case where there
    is a name in backzone/ that does not occur as a link
    in the remaining data.

    Michael Deckers.