[tz] Add new timezone for Hanoi Capital, Vietnam

[Guy Harris]

On Feb 18, 2019, at 10:22 AM, KP <khaiphan9x at gmail.com> wrote:

> Timezones used in Vietnam are +7:00, +8:00, +9:00 instead of +7:00 only like Bangkok, Thailand

...prior to 1970-01-01 00:00:00.  That's why Asia/Hanoi is in backzone rather than asia.