fix integer datetime division rounding error

The attached patch seems to fix the rounding error that is causing
regression failures on machines with integer datetimes. (Source of error
discovered by Andrew@Supernews).ISTM this code needs to be given some
careful analysis - I know it makes my head spin reading it.

cheers

andrew
Index: src/backend/utils/adt/timestamp.c
===================================================================
RCS file: /home/cvsmirror/pgsql/src/backend/utils/adt/timestamp.c,v
retrieving revision 1.145
diff -c -r1.145 timestamp.c
*** src/backend/utils/adt/timestamp.c   23 Jul 2005 14:53:21 -0000      1.145
--- src/backend/utils/adt/timestamp.c   24 Jul 2005 00:04:08 -0000
***************
*** 2319,2325 ****
        day_remainder += (month_remainder * DAYS_PER_MONTH) - (int)(month_remainder * DAYS_PER_MONTH);

  #ifdef HAVE_INT64_TIMESTAMP
!       result->time += day_remainder * USECS_PER_DAY;
  #else
        result->time += day_remainder * SECS_PER_DAY;
        result->time = JROUND(result->time);
--- 2319,2325 ----
        day_remainder += (month_remainder * DAYS_PER_MONTH) - (int)(month_remainder * DAYS_PER_MONTH);

  #ifdef HAVE_INT64_TIMESTAMP
!       result->time += rint(day_remainder * USECS_PER_DAY);
  #else
        result->time += day_remainder * SECS_PER_DAY;
        result->time = JROUND(result->time);