Sync zoneinfo database with tzdata2015a from ftp://ftp.iana.org/tz/releases

Sync zoneinfo database with tzdata2015a from ftp://ftp.iana.org/tz/releases

Changes affecting future time stamps

* The Mexican state of Quintana Roo, represented by America/Cancun,
    will shift from Central Time with DST to Eastern Time without DST
    on 2015-02-01 at 02:00.  (Thanks to Steffen Thorsen and Gwillim Law.)

* Chile will not change clocks in April or thereafter; its new standard time
    will be its old daylight saving time.  This affects America/Santiago,
    Pacific/Easter, and Antarctica/Palmer.  (Thanks to Juan Correa.)

* New leap second 2015-06-30 23:59:60 UTC as per IERS Bulletin C 49.
    (Thanks to Tim Parenti.)

Changes affecting past time stamps

* Iceland observed DST in 1919 and 1921, and its 1939 fallback
    transition was Oct. 29, not Nov. 29.  Remove incorrect data from
    Shanks about time in Iceland between 1837 and 1908.

* Some more zones have been turned into links, when they differed
    from existing zones only for older time stamps.  As usual,
    these changes affect UTC offsets in pre-1970 time stamps only.
    The affected zones are: Asia/Aden, Asia/Bahrain, Asia/Kuwait,
    and Asia/Muscat.

Changes affecting commentary

* The leapseconds file commentary now mentions the expiration date.
    (Problem reported by Martin Burnicki.)

* Update Mexican Library of Congress URL.