[tz] 1981/2 Singapore+Malaysia switch from GMT+0730 to GMT+0800

[Robert Elz]

Unless I missed something, that patch only altered Asia/Singapore.
I'd be truly astounded if the same was not also required for
Asia/Kuala_Lumpur.

Here:
   https://www.therakyatpost.com/living/2021/04/09/the-forgotten-history-of-malaysias-6-timezone-changes/

it says:
   Dr Mahathir [PM at the time] passed the Malaysian Standard Time Act (1981),
   which set the clocks ahead 30 minutes on 11.30pm December 31st 1981.
   New Year\u2019s celebrations came early that year.   

There's also a summary of the earlier changes, but nothing we didn't
already know, and no additional details on exact transition times/dates.

kre