pgsql: Update time zone data files to tzdata release 2019a.

Update time zone data files to tzdata release 2019a.

DST law changes in Palestine and Metlakatla.
Historical corrections for Israel.

Etc/UCT is now a backward-compatibility link to Etc/UTC, instead
of being a separate zone that generates the abbreviation "UCT",
which nowadays is typically a typo.  Postgres will still accept
"UCT" as an input zone name, but it won't output it.

Branch
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REL9_6_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/b25a81c7111724dd69449bdae000cee6ee4ecc98

Modified Files
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src/timezone/data/tzdata.zi    | 14 +++++++++-----
src/timezone/known_abbrevs.txt |  1 -
2 files changed, 9 insertions(+), 6 deletions(-)