Update time zone data files to tzdata release 2018e.

This commit pulls in the latest tzdata from Postgres 11. We
intentionally left out comment changes to
`src/backend/utils/adt/datetime.c` because it's not applicable (yet).

> DST law changes in North Korea.  Redefinition of "daylight savings" in
> Ireland, as well as for some past years in Namibia and Czechoslovakia.
> Additional historical corrections for Czechoslovakia.
>
> With this change, the IANA database models Irish timekeeping as following
> "standard time" in summer, and "daylight savings" in winter, so that the
> daylight savings offset is one hour behind standard time not one hour
> ahead.  This does not change their UTC offset (+1:00 in summer, 0:00 in
> winter) nor their timezone abbreviations (IST in summer, GMT in winter),
> though now "IST" is more correctly read as "Irish Standard Time" not "Irish
> Summer Time".  However, the "is_dst" column in the pg_timezone_names view
> will now be true in winter and false in summer for the Europe/Dublin zone.
>
> Similar changes were made for Namibia between 1994 and 2017, and for
> Czechoslovakia between 1946 and 1947.
>
> So far as I can find, no Postgres internal logic cares about which way
> tm_isdst is reported; in particular, since commit b2cbced9 we do not
> rely on it to decide how to interpret ambiguous timestamps during DST
> transitions.  So I don't think this change will affect any Postgres
> behavior other than the timezone-view outputs.
>
> Discussion: https://postgr.es/m/30996.1525445902@sss.pgh.pa.us
(cherry picked from commit 234bb985)
Co-authored-by: NJesse Zhang <sbjesse@gmail.com>
Co-authored-by: NTaylor Vesely <tvesely@pivotal.io>

src/timezone/known_abbrevs.txt

@@ -70,15 +70,15 @@ EEST	10800	D
 EET	7200
 EST	-18000
 GMT	0
+GMT	0	D
 HDT	-32400	D
 HKT	28800
 HST	-36000
 IDT	10800	D
 IST	19800
-IST	3600	D
+IST	3600
 IST	7200
 JST	32400
-KST	30600
 KST	32400
 MDT	-21600	D
 MEST	7200	D

src/timezone/tznames/Asia.txt

@@ -118,13 +118,13 @@ IRST    Asia/Tehran  # Iran Standard Time (obsolete)
 IRT     12600    # Iran Time (not in IANA database)
 # CONFLICT! IST is not unique
 # Other timezones:
-# - IST: Irish Summer Time (Europe)
+# - IST: Irish Standard Time (Europe)
 # - IST: Israel Standard Time (Asia)
 IST     19800    # Indian Standard Time
                  #     (Asia/Calcutta)
 # CONFLICT! IST is not unique
 # Other timezones:
-# - IST: Irish Summer Time (Europe)
+# - IST: Irish Standard Time (Europe)
 # - IST: Indian Standard Time (Asia)
 IST      7200    # Israel Standard Time
                  #     (Asia/Jerusalem)

src/timezone/tznames/Default

@@ -236,7 +236,7 @@ IRKT    Asia/Irkutsk  # Irkutsk Time (obsolete)
 IRT     12600    # Iran Time (not in IANA database)
 # CONFLICT! IST is not unique
 # Other timezones:
-# - IST: Irish Summer Time (Europe)
+# - IST: Irish Standard Time (Europe)
 # - IST: Indian Standard Time (Asia)
 IST      7200    # Israel Standard Time
                  #     (Asia/Jerusalem)

src/timezone/tznames/Europe.txt

@@ -180,7 +180,7 @@ GMT         0    # Greenwich Mean Time
 # Other timezones:
 # - IST: Indian Standard Time (Asia)
 # - IST: Israel Standard Time (Asia)
-IST      3600 D  # Irish Summer Time
+IST      3600    # Irish Standard Time
                  #     (Europe/Dublin)
 MEST     7200 D  # Middle Europe Summer Time
                  #     (MET)