[tz] Change DTS and time zone for Morocco

[liuchao (CR)]

In the past, Morocco observed four clock changes per year. Like in most other countries with seasonal time changes, the DST period in Morocco started in the spring and ended in the fall (autumn). However, clocks were turned back to standard time during the Islamic month of Ramadan to make it easier to observe the daytime fast. The Kingdom of Morocco now remains permanently set to UTC+01:00 instead of following an earlier plan to return to UTC+00:00 on October 28, 2018. But the data in Africa doesn't change. There still are four clock changes in 2018, which causes isdst flag error in 2019.
https://support.microsoft.com/en-us/help/4468323/dst-and-time-zone-changes-in-windows-for-morocco-and-volgograd
https://www.timeanddate.com/news/time/morocco-abolishes-time-changes.html
Before change,
[cid:image001.png at 01D59979.EB9BDA90]
on May 5 2019, the time jumps from 02:59:59 to 02:00:00, the isdst flag should change from 1 to 0.
After change,
[cid:image002.png at 01D59979.EB9BDA90]
When dataform is rearguard, it is fixed via ziguard.awk,
[cid:image003.png at 01D5997A.49F01BB0]
However, I don't understand why it's only changed in rearguard format.
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