date overflows

I'm seeing some date input overflows here.   I tested on CVS HEAD
without --enable-integer-datetimes and 7.4.9 and 8.0.4 with
--enable-integer-datetimes, so it appears to have been around for a
while:

jurka=# select '111123456-01-01'::date;
      date
---------------
  5290466-07-05
(1 row)

jurka=# select '14824-01-01 BC'::date;
       date
----------------
  11744398-01-21
(1 row)