tzcode: update to 2017b

tzcode: update to 2017b

 Briefly: Haiti has resumed DST.

  Changes to past and future time stamps

    Haiti resumed observance of DST in 2017.  (Thanks to Steffen Thorsen.)

  Changes to past time stamps

    Liberia changed from -004430 to +00 on 1972-01-07, not 1972-05-01.

    Use "MMT" to abbreviate Liberia's time zone before 1972, as "-004430"
    is one byte over the POSIX limit.  (Problem reported by Derick Rethans.)

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