[pgpool-committers: 6600] pgpool: Doc: enhance installation documents.

[Tatsuo Ishii]

Doc: enhance installation documents.

Add "Planning" section so that uses can grasp a big picture of
installation.

Branch
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V4_1_STABLE

Details
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https://git.postgresql.org/gitweb?p=pgpool2.git;a=commitdiff;h=ffb3c59c83815cd24e6135e9251b392fcaadf952

Modified Files
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doc.ja/src/sgml/installation.sgml |  54 ++++++++++++++++++++
doc/src/sgml/installation.sgml    | 103 ++++++++++++++++++++++++++++++++++++--
2 files changed, 152 insertions(+), 5 deletions(-)