Update timezone code from tzcode 2013i.
Now we have Paul's support for version-3 tz files checked in, this
patch updates all the code we take (unmodified) from tzcode to version
2013i (which includes the support for generating version-3 tz files
where necessary).
Tested x86_64.
* timezone/checktab.awk: Update from tzcode 2013i.
* timezone/private.h: Likewise.
* timezone/scheck.c: Likewise.
* timezone/tzfile.h: Likewise.
* timezone/tzselect.ksh: Likewise.
* timezone/zdump.c: Likewise.
* timezone/zic.c: Likewise.