pgsql: Allow to_char(interval) and to_char(time) to use AM/PM

Log Message:
-----------
Allow to_char(interval) and to_char(time) to use AM/PM specifications.
Map them to a single day, so '30 hours' is 'AM'.

Have to_char(interval) and to_char(time) use "HH", "HH12" as 12-hour
intervals, rather than bypass and print the full interval hours. This
is neeeded because to_char(time) is mapped to interval in this function.
Intervals should use "HH24", and document suggestion.

Allow "D" format specifiers for interval/time.

Tags:
----
REL8_1_STABLE

Modified Files:
--------------
pgsql/doc/src/sgml:
func.sgml (r1.291.2.2 -> r1.291.2.3)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/func.sgml.diff?r1=1.291.2.2&r2=1.291.2.3)
pgsql/src/backend/utils/adt:
formatting.c (r1.101.2.1 -> r1.101.2.2)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/formatting.c.diff?r1=1.101.2.1&r2=1.101.2.2)