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_1_STABLE

Details
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http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=10fbaf0f94544f97f74caefac81f9a9720999840

Modified Files
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doc/src/sgml/release-7.4.sgml | 101 ++++++++++++++++++++-
doc/src/sgml/release-8.0.sgml | 171 +++++++++++++++++++++++++++++++++-
doc/src/sgml/release-8.1.sgml | 207 ++++++++++++++++++++++++++++++++++++++---
3 files changed, 462 insertions(+), 17 deletions(-)