pgsql: Update 9.1 release notes to reflect commits through today.

Update 9.1 release notes to reflect commits through today.

Also do another pass of copy-editing.

Branch
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REL9_1_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/f85e4057cfe62752eb57d2315d4acda5bb5c1e9e

Modified Files
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doc/src/sgml/release-9.1.sgml | 151 +++++++++++++++++++++++++++--------------
1 files changed, 99 insertions(+), 52 deletions(-)