pgsql: When checking for datetime field overflow, we should allow a

Log Message:
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When checking for datetime field overflow, we should allow a fractional-second
part that rounds up to exactly 1.0 second. The previous coding rejected input
like "00:12:57.9999999999999999999999999999", with the exact number of nines
needed to cause failure varying depending on float-timestamp option and
possibly on platform. Obviously this should round up to the next integral
second, if we don't have enough precision to distinguish the value from that.
Per bug #4789 from Robert Kruus.

In passing, fix a missed check for fractional seconds in one copy of the
"is it greater than 24:00:00" code.

Broken all the way back, so patch all the way back.

Modified Files:
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pgsql/src/backend/utils/adt:
datetime.c (r1.203 -> r1.204)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/datetime.c?r1=1.203&r2=1.204)