tzdata: update to 2015b

Changes affecting future time stamps

Mongolia will start observing DST again this year, from the last
Saturday in March at 02:00 to the last Saturday in September at 00:00.
(Thanks to Ganbold Tsagaankhuu.)

Palestine will start DST on March 28, not March 27.  Also,
correct the fall 2014 transition from September 26 to October 24.
Adjust future predictions accordingly.  (Thanks to Steffen Thorsen.)

Changes affecting past time stamps

The 1982 zone shift in Pacific/Easter has been corrected, fixing a 2015a
regression.  (Thanks to Stuart Bishop for reporting the problem.)

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.
Their old contents have been moved to the 'backzone' file.
The affected zones are: America/Antigua, America/Cayman,
Pacific/Midway, and Pacific/Saipan.

Changes affecting time zone abbreviations

Correct the 1992-2010 DST abbreviation in Volgograd from "MSK" to "MSD".
(Thanks to Hank W.)

(From OE-Core rev: b0053928)

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