pgsql: Update release notes for releases 9.0.1, 8.4.5, 8.3.12, 8.2.18,

Update release notes for releases 9.0.1, 8.4.5, 8.3.12, 8.2.18, 8.1.22,
8.0.26, and 7.4.30.

Branch
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REL8_0_STABLE

Details
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http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=5da1406e7027e1418d389911127f257cf129707a

Modified Files
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doc/src/sgml/release-7.4.sgml | 101 ++++++++++++++++++++++++-
doc/src/sgml/release-8.0.sgml | 171 ++++++++++++++++++++++++++++++++++++++++-
2 files changed, 268 insertions(+), 4 deletions(-)