pgbouncer - pgbouncer: tcp_defer_accept improvements.

Log Message:
-----------
tcp_defer_accept improvements.

- support freebsd accept filter
- remove user control of actual value, as its basically undocumented
- allow online setting change

Modified Files:
--------------
    pgbouncer/src:
        main.c (r1.35 -> r1.36)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgbouncer/pgbouncer/src/main.c.diff?r1=1.35&r2=1.36)
        pooler.c (r1.11 -> r1.12)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgbouncer/pgbouncer/src/pooler.c.diff?r1=1.11&r2=1.12)
    pgbouncer/include:
        pooler.h (r1.3 -> r1.4)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgbouncer/pgbouncer/include/pooler.h.diff?r1=1.3&r2=1.4)