[pgpool-committers: 3700] pgpool: Add release 3.1-3.6 release notes.

[Tatsuo Ishii]

Add release 3.1-3.6 release notes.

The contents are not accurate at this moment except 3.6.1. They are
just copy of 3.5.5 release note.

Branch
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master

Details
-------
http://git.postgresql.org/gitweb?p=pgpool2.git;a=commitdiff;h=b23d45c35c53ce6deb77c6f8d7dbacfe067fcd77

Modified Files
--------------
doc/src/sgml/filelist.sgml    |   4 +
doc/src/sgml/release-3.1.sgml | 392 ++++++++++++++++++++++++++++++++++++++++++
doc/src/sgml/release-3.2.sgml | 392 ++++++++++++++++++++++++++++++++++++++++++
doc/src/sgml/release-3.3.sgml | 392 ++++++++++++++++++++++++++++++++++++++++++
doc/src/sgml/release-3.4.sgml | 392 ++++++++++++++++++++++++++++++++++++++++++
doc/src/sgml/release-3.5.sgml |  18 +-
doc/src/sgml/release-3.6.sgml | 205 ++++++++++++++++++++++
doc/src/sgml/release.sgml     |   4 +
8 files changed, 1798 insertions(+), 1 deletion(-)