replace library time handling functions

mktime, tzset, asctime, ctime, gmtime, localtime, strftime
with zoneinfo implementations in src/commands/zoneinfo, referenced
from src/lib/stdtime/Makefile.in.

include/sys/time.h

@@ -14,6 +14,11 @@ struct timeval
 	long /*useconds_t*/ tv_usec;
 };
 
+struct timezone {
+	int     tz_minuteswest; /* minutes west of Greenwich */
+	int     tz_dsttime;     /* type of dst correction */
+};
+
 int gettimeofday(struct timeval *_RESTRICT tp, void *_RESTRICT tzp);
 
 /* Compatibility with other Unix systems */