Fix for interval division/multiplication

I working on the 'date' interval patch, I found a bug in handling of
interval division and multiplication. Look at this:

test=> select '4 months'::interval / 5;
?column?
---------------
1 mon -6 days
(1 row)

With the attached fix, it returns the right value:

test=> select '4 months'::interval / 5;
?column?
----------
24 days
(1 row)

The bug is the use of rint() to round the division, but then using the
rounded value to find the remainder to pass down to the time field.

The attached patch has been applied to current CVS. Should I backpatch
this fix?

--
Bruce Momjian | http://candle.pha.pa.us
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