pgsql: Add backend and pg_dump code to allow preservation of pg_enum

Log Message:
-----------
Add backend and pg_dump code to allow preservation of pg_enum oids, for
use in binary upgrades.

Bump catalog version for detection by pg_migrator of new backend API.

Modified Files:
--------------
    pgsql/src/backend/catalog:
        pg_enum.c (r1.11 -> r1.12)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/pg_enum.c?r1=1.11&r2=1.12)
    pgsql/src/backend/commands:
        typecmds.c (r1.141 -> r1.142)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/typecmds.c?r1=1.141&r2=1.142)
    pgsql/src/bin/pg_dump:
        pg_dump.c (r1.562 -> r1.563)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_dump.c?r1=1.562&r2=1.563)
    pgsql/src/include/catalog:
        catversion.h (r1.560 -> r1.561)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h?r1=1.560&r2=1.561)
        pg_enum.h (r1.5 -> r1.6)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_enum.h?r1=1.5&r2=1.6)