[pgpool-general: 6561] Doc: Add general description of failover

[Tatsuo Ishii]

Hi,

I have added $subject to upcoming Pgpool-II 4.1 docs.
In
http://tatsuo-ishii.github.io/pgpool-II/current/runtime-config-failover.html
"5.9. Failover and Failback".

Comments and suggestions are welcome (I am sure I made a mistake
somewhere because I am not a native English speaker).

Best regards,
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese:http://www.sraoss.co.jp