* libc/include/time.h (__tzrule_struct): Make offset long, since
a 16-bit int overflows on a 12-hour offset.
* libc/sys/linux/include/time.h: Ditto.
* libc/time/mktime.c (mktime): Use new type of __tzrule.offset.
* libc/time/mktm_r.c: Ditto.
* libc/time/gettzinfo.c: Ditto.
* libc/time/strftime.c (strftime): Fix '%x' to deal with negative
years. Fix '%z' to use long, not int.
* libc/include/time.h [!CYGWIN](_timezone): Change to long.
(__tzrule_type, __tzinfo_type): New types.
(__gettzinfo): New function.
* libc/sys/linux/include/time.h: Ditto.
* libc/time/Makefile.am: Add gettzinfo.c.
* libc/time/Makefile.in: Regenerated.
* libc/time/local.h: Moved __tzrule_type to time.h.
* libc/time/mktime.c: Call __gettzinfo to reference
__tznorth, __tzyear, and __tzrule array.
* libc/time/mktm_r.c: Ditto.
* libc/time/strftime.c: Ditto.
* libc/time/tzset_r.c: Ditto. Also remove definition
of __tzrule which is now in gettzinfo.c. Change _timezone
references to not cast to time_t.
* libc/time/gettzinfo.c: New file.
