pgbouncer - pgbouncer: Cmdline option and config param to support user

Log Message:
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Cmdline option and config param to support user switching.

Original patch from Jason Coby, applied with minor modifications.

Tags:
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pgbouncer_1_1_stable

Modified Files:
--------------
    pgbouncer/doc:
        config.txt (r1.3.2.2 -> r1.3.2.3)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgbouncer/pgbouncer/doc/config.txt.diff?r1=1.3.2.2&r2=1.3.2.3)
        usage.txt (r1.2.2.1 -> r1.2.2.2)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgbouncer/pgbouncer/doc/usage.txt.diff?r1=1.2.2.1&r2=1.2.2.2)
    pgbouncer/src:
        main.c (r1.18.2.1 -> r1.18.2.2)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgbouncer/pgbouncer/src/main.c.diff?r1=1.18.2.1&r2=1.18.2.2)
        system.c (r1.1 -> r1.1.4.1)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgbouncer/pgbouncer/src/system.c.diff?r1=1.1&r2=1.1.4.1)
        system.h (r1.5 -> r1.5.2.1)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgbouncer/pgbouncer/src/system.h.diff?r1=1.5&r2=1.5.2.1)