txdata: update to 2015c

Changes affecting future time stamps

Egypt's spring-forward transition is at 24:00 on April's last Thursday,
not 00:00 on April's last Friday.  2015's transition will therefore be on
Thursday, April 30 at 24:00, not Friday, April 24 at 00:00.  Similar fixes
apply to 2026, 2037, 2043, etc.  (Thanks to Steffen Thorsen.)

Changes affecting past time stamps

The following changes affect some pre-1991 Chile-related time stamps
in America/Santiago, Antarctica/Palmer, and Pacific/Easter.

The 1910 transition was January 10, not January 1.

The 1918 transition was September 10, not September 1.

The UTC-4 time observed from 1932 to 1942 is now considered to be
standard time, not year-round DST.

Santiago observed DST (UTC-3) from 1946-07-15 through 1946-08-31,
then reverted to standard time, then switched its time zone to
UTC-5 on 1947-04-01.

Assume transitions before 1968 were at 00:00, since we have no data
saying otherwise.

The spring 1988 transition was 1988-10-09, not 1988-10-02.
The fall 1990 transition was 1990-03-11, not 1990-03-18.

Assume no UTC offset change for Pacific/Easter on 1890-01-01,
and omit all transitions on Pacific/Easter from 1942 through 1946
since we have no data suggesting that they existed.

One more zone has been turned into a link, as it differed
from an existing zone only for older time stamps.  As usual,
this change affects UTC offsets in pre-1970 time stamps only.
The zone's old contents have been moved to the 'backzone' file.
The affected zone is America/Montreal.

Signed-off-by: Armin Kuster <akuster808@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>