Port to x32 by fixing type incompatibility with POSIX.

Reported by Elliott Hughes in
<http://mm.icann.org/pipermail/tz/2013-September/020376.html>.
* localtime.c (timezone) [USG_COMPAT]:
(altzone) [ALTZONE]: Now long, not time_t.
* strftime.c (_fmt): Use long, not int, to store timezone.
* NEWS: Document this.