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

Update time zone data files to tzdata release 2018c.

DST law changes in Brazil, Sao Tome and Principe. Historical corrections
for Bolivia, Japan, and South Sudan. The "US/Pacific-New" zone has been
removed (it was only a link to America/Los_Angeles anyway).

Branch
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REL9_6_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/462402be873dfa252c8ab34ff42a7af252cfa481

Modified Files
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src/timezone/data/tzdata.zi | 22 +++++++++++++---------
src/timezone/known_abbrevs.txt | 1 -
src/timezone/tznames/Africa.txt | 3 +--
3 files changed, 14 insertions(+), 12 deletions(-)