[pgpool-committers: 9534] pgpool: Doc: add release notes.

[Chen Ningwei]

Doc: add release notes.

Branch
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V4_0_STABLE

Details
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https://git.postgresql.org/gitweb?p=pgpool2.git;a=commitdiff;h=a277e819316891fb05cc86de955f7c2a8027cb29

Modified Files
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doc.ja/src/sgml/release-4.0.sgml | 110 ++++++++++++++++++++++++++++++++++++
doc/src/sgml/release-4.0.sgml    | 117 +++++++++++++++++++++++++++++++++++++++
2 files changed, 227 insertions(+)