pgsql: Add items: > * Prevent to_char() on interval from returning

Log Message:
-----------
Add items:

> * 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.
>

Modified Files:
--------------
pgsql/doc:
TODO (r1.1519 -> r1.1520)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/TODO.diff?r1=1.1519&r2=1.1520)
pgsql/doc/src/FAQ:
TODO.html (r1.26 -> r1.27)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/FAQ/TODO.html.diff?r1=1.26&r2=1.27)