We currently overflow due to wrong types used internally in rtc_mktime,
on all platforms, and we return a too small type on 32-bit.
One consumer that directly benefits from this is mktime64. Many others
may still store the result in a wrong type.
While at it, drop the redundant cast of mon in rtc_mktime (obsoleted by
714209832d).
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
90c52423be