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.