ICU time zone data patch

This folder contains tzdata package patched by ICU development.

• tzdata2021a1.tar.gz: tzdata2021a + tzdata2021b changes except pre-1970 zone merges
• tzdata2021a2.tar.gz: tzdata2021a1 + tzdata2021d changes
• tzdata2021a3.tar.gz: tzdata2021a2 + tzdata2021e changes
• tzdata2021a4.tar.gz: tzdata2021a3 + fix for ICU-21825