[tz] North Vietnam 1970 to 1975 - Asia/Hanoi belongs into main file

[Michael H Deckers]

    On 2020-06-30 09:20, Alois Treindl wrote:

> That problem would easily be fixed if Asia/Hanoi were moved from 
> backzone to file asia.


    ...or if Asia/Hanoi were made a link to Asia/Bangkok (as
    Asia/Vientiane and Asia/Phnom_Penh already are).

    Michael Deckers.