pgsql: Update time zone data files to tzdata release 2018f.

Update time zone data files to tzdata release 2018f.

DST law changes in Chile, Fiji, and Russia (Volgograd).
Historical corrections for China, Japan, Macau, and North Korea.

Note: like the previous tzdata update, this involves a depressingly
large amount of semantically-meaningless churn in tzdata.zi.  That
is a consequence of upstream's data compression method assigning
unstable abbreviations to DST rulesets.  I complained about that
to them last time, and this version now uses an assignment method
that pays some heed to not changing abbreviations unnecessarily.
So hopefully, that'll be better going forward.

Branch
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REL9_6_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/185f135c91e907e7ac27a0e1d1ef27e2c1d189e7

Modified Files
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src/timezone/data/tzdata.zi      | 5273 +++++++++++++++++++-------------------
src/timezone/known_abbrevs.txt   |    1 +
src/timezone/tznames/America.txt |    3 +
src/timezone/tznames/Asia.txt    |    4 +
src/timezone/tznames/Default     |    3 +
src/timezone/tznames/Pacific.txt |    3 +
6 files changed, 2660 insertions(+), 2627 deletions(-)