pgsql: Change the parameter_types column of the pg_prepared_statements

Log Message:
-----------
Change the parameter_types column of the pg_prepared_statements to be
an array of regtype, rather than an array of OIDs. This is likely to
be more useful to user, and the type OID can easily be obtained by
casting a regtype value to OID. Per suggestion from Tom.

Update the documentation and regression tests, and bump the catversion.

Modified Files:
--------------
    pgsql/doc/src/sgml:
        catalogs.sgml (r2.116 -> r2.117)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/catalogs.sgml.diff?r1=2.116&r2=2.117)
    pgsql/src/backend/catalog:
        system_views.sql (r1.23 -> r1.24)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/system_views.sql.diff?r1=1.23&r2=1.24)
    pgsql/src/backend/commands:
        prepare.c (r1.45 -> r1.46)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/prepare.c.diff?r1=1.45&r2=1.46)
    pgsql/src/include/catalog:
        catversion.h (r1.310 -> r1.311)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h.diff?r1=1.310&r2=1.311)
        pg_type.h (r1.168 -> r1.169)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_type.h.diff?r1=1.168&r2=1.169)
    pgsql/src/test/regress/expected:
        prepare.out (r1.7 -> r1.8)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/prepare.out.diff?r1=1.7&r2=1.8)
        rules.out (r1.111 -> r1.112)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/rules.out.diff?r1=1.111&r2=1.112)