Add items from Tom:

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