Log Message:
-----------
Add comments abount failover_command and failback_command.
Modified Files:
--------------
pgpool-II:
pgpool.conf.sample (r1.7 -> r1.8)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgpool/pgpool-II/pgpool.conf.sample.diff?r1=1.7&r2=1.8)