pgsql: Fix to_timestamp() to not require upper/lower case matching for

Log Message:
-----------
Fix to_timestamp() to not require upper/lower case matching for meridian
designations (AM/PM).  Also separate out matching of a meridian with
periods (e.g. A.M.) and with those without.

Do the same for AD/BC.

Brendan Jurd

Modified Files:
--------------
    pgsql/doc/src/sgml:
        func.sgml (r1.471 -> r1.472)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/func.sgml?r1=1.471&r2=1.472)
    pgsql/src/backend/utils/adt:
        formatting.c (r1.153 -> r1.154)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/formatting.c?r1=1.153&r2=1.154)
    pgsql/src/test/regress/expected:
        horology.out (r1.69 -> r1.70)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/horology.out?r1=1.69&r2=1.70)
    pgsql/src/test/regress/sql:
        horology.sql (r1.35 -> r1.36)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/horology.sql?r1=1.35&r2=1.36)