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

Log Message:
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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.

Modified Files:
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    pgsql/doc/src/sgml:
        func.sgml (r1.296 -> r1.297)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/func.sgml.diff?r1=1.296&r2=1.297)
    pgsql/src/backend/utils/adt:
        formatting.c (r1.102 -> r1.103)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/formatting.c.diff?r1=1.102&r2=1.103)