pgbouncer - pgbouncer: some more cleanups: - avoid NULL values for

Log Message:
-----------
some more cleanups:

- avoid NULL values for config variables
- cf_shutdown=2 means fast shutdown
- export cf_config_file

Modified Files:
--------------
    pgbouncer/include:
        bouncer.h (r1.23 -> r1.24)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgbouncer/pgbouncer/include/bouncer.h.diff?r1=1.23&r2=1.24)
    pgbouncer/src:
        admin.c (r1.39 -> r1.40)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgbouncer/pgbouncer/src/admin.c.diff?r1=1.39&r2=1.40)
        janitor.c (r1.32 -> r1.33)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgbouncer/pgbouncer/src/janitor.c.diff?r1=1.32&r2=1.33)
        main.c (r1.59 -> r1.60)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgbouncer/pgbouncer/src/main.c.diff?r1=1.59&r2=1.60)
        util.c (r1.31 -> r1.32)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgbouncer/pgbouncer/src/util.c.diff?r1=1.31&r2=1.32)