pgsql: Add items from Tom: < o Add a GUC variable to allow output of

Log Message:
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Add items from Tom:

< o Add a GUC variable to allow output of interval values in ISO8601
< format
212a211,223
> o Add a GUC variable to allow output of interval values in ISO8601
> format
> o Improve timestamptz subtraction to be DST-aware
>
> Currently, subtracting one date from another that crosses a
> daylight savings time adjustment can return '1 day 1 hour', but
> adding that back to the first date returns a time one hour in
> the future. This is caused by the adjustment of '25 hours' to
> '1 day 1 hour', and '1 day' is the same time the next day, even
> if daylight savings adjustments are involved.
>
> o Fix interval display to support values exceeding 2^31 hours
> o Add overflow checking to timestamp and interval arithmetic

Modified Files:
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pgsql/doc:
TODO (r1.1693 -> r1.1694)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/TODO.diff?r1=1.1693&r2=1.1694)
pgsql/doc/src/FAQ:
TODO.html (r1.200 -> r1.201)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/FAQ/TODO.html.diff?r1=1.200&r2=1.201)