doc

> * Prevent to_char() on interval from returning meaningless values
>
>   For example, to_char('1 month', 'mon') is meaningless.  Basically,
>   most date-related parameters to to_char() are meaningless for
>   intervals because interval is not anchored to a date.
>
> * Allow to_char() on interval values to accumulate the highest unit
>   requested
>
> 	o to_char(INTERVAL '1 hour 5 minutes', 'MI') => 65
> 	o to_char(INTERVAL '43 hours 20 minutes', 'MI' ) => 2600
> 	o to_char(INTERVAL '43 hours 20 minutes', 'WK:DD:HR:MI') => 0:1:19:20
> 	o to_char(INTERVAL '3 years 5 months','MM') => 41
>
>   Some special format flag would be required to request such
>   accumulation.  Such functionality could also be added to EXTRACT.
>   Prevent accumulation that crosses the month/day boundary because of
>   the uneven number of days in a month.
>