pgbouncer - pgbouncer: Make listen(2) backlog argument configurable.

Log Message:
-----------
Make listen(2) backlog argument configurable.

Modified Files:
--------------
    pgbouncer/doc:
        config.txt (r1.23 -> r1.24)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgbouncer/pgbouncer/doc/config.txt?r1=1.23&r2=1.24)
    pgbouncer/etc:
        pgbouncer.ini (r1.10 -> r1.11)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgbouncer/pgbouncer/etc/pgbouncer.ini?r1=1.10&r2=1.11)
    pgbouncer/include:
        bouncer.h (r1.27 -> r1.28)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgbouncer/pgbouncer/include/bouncer.h?r1=1.27&r2=1.28)
    pgbouncer/src:
        main.c (r1.64 -> r1.65)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgbouncer/pgbouncer/src/main.c?r1=1.64&r2=1.65)
        pooler.c (r1.20 -> r1.21)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgbouncer/pgbouncer/src/pooler.c?r1=1.20&r2=1.21)