Sync zoneinfo database with tzdata2017a from ftp://ftp.iana.org/tz/releases

Sync zoneinfo database with tzdata2017a from ftp://ftp.iana.org/tz/releases

* Mongolia no longer observes DST.  (Thanks to Ganbold Tsagaankhuu.)

* Chile's Region of Magallanes moves from -04/-03 to -03 year-round.
    Its clocks diverge from America/Santiago starting 2017-05-13 at
    23:00, hiving off a new zone America/Punta_Arenas.  Although the
    Chilean government says this change expires in May 2019, for now
    assume it's permanent.  (Thanks to Juan Correa and Deborah
    Goldsmith.)  This also affects Antarctica/Palmer.

* Fix many entries for historical time stamps for Europe/Madrid
    before 1979, to agree with tables compiled by Pere Planesas of the
    National Astronomical Observatory of Spain.  As a side effect,
    this changes some time stamps for Africa/Ceuta before 1929, which
    are probably guesswork anyway.  (Thanks to Steve Allen and
    Pierpaolo Bernardi for the heads-ups, and to Michael Deckers for
    correcting the 1901 transition.)

* Ecuador observed DST from 1992-11-28 to 1993-02-05.
    (Thanks to Alois Treindl.)

* Asia/Atyrau and Asia/Oral were at +03 (not +04) before 1930-06-21.
    (Thanks to Stepan Golosunov.)

* Switch to numeric time zone abbreviations for South America, as
    part of the ongoing project of removing invented abbreviations.
    This avoids the need to invent an abbreviation for the new Chilean
    zone.  Similarly, switch from invented to numeric time zone
    abbreviations for a number of other zones.

* For Alaska time from 1900 through 1967, instead of "CAT" use the
    abbreviation "AST", the abbreviation commonly used at the time
    (Atlantic Standard Time had not been standardized yet).  Use "AWT"
    and "APT" instead of the invented abbreviations "CAWT" and "CAPT".

* Use "CST" and "CDT" instead of invented abbreviations for Macau
    before 1999 and Taiwan before 1938, and use "JST" instead of the
    invented abbreviation "JCST" for Japan and Korea before 1938.

* Move the Pacific/Johnston link from 'australasia' to 'backward',
    since Johnston is now uninhabited.

* africa (Africa/Monrovia): The 1972 transition was on January 7,
    not May 1.  (Shanks was wrong again! and Howse was right.)

* The 'Theory' file now better documents choice of historical time
    zone abbreviations.  (Problems reported by Michael Deckers.)