pgbouncer - pgbouncer: sync some doc fixes from -stable

Log Message:
-----------
sync some doc fixes from -stable

Modified Files:
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pgbouncer/doc:
config.txt (r1.8 -> r1.9)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgbouncer/pgbouncer/doc/config.txt.diff?r1=1.8&r2=1.9)
usage.txt (r1.4 -> r1.5)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgbouncer/pgbouncer/doc/usage.txt.diff?r1=1.4&r2=1.5)