libc: Sync asctime.c and localtime.c with tzcode2010a from elsie.

libc: Sync asctime.c and localtime.c with tzcode2010a from elsie.

asctime.c:   Set errno to EINVAL and return "??? ??? ?? ??:??:?? ????\n" if
             asctime_r() is called with a NULL struct tm pointer.
             (Note that asctime_r() is called by ctime_r() and asctime();
             asctime() is called by ctime().)

localtime.c: Set errno to EINVAL and return WRONG if time1() is called with
             a NULL struct tm pointer; avoid dereference if a NULL struct
             tm pointer is passed to timelocal(), timegm(), or timeoff().
             (Note that time1 is called by mktime(), timegm(), and timeoff();
             mktime is called by timelocal().)