[pgpool-committers: 9090] pgpool: Doc: Add release notes.

[Bo Peng]

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=9cbcdfafebd895ea05ef11f77edef3253dc1c8a0

Modified Files
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doc.ja/src/sgml/release-4.0.sgml | 165 +++++++++++++++++++++++++++++++++
doc/src/sgml/release-4.0.sgml    | 194 +++++++++++++++++++++++++++++++++++++++
2 files changed, 359 insertions(+)