pgsql: Update 9.3 release notes.

Update 9.3 release notes.

Some corrections, a lot of copy-editing.

Set projected release date as 2013-09-09.

Branch
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REL9_3_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/3234a64f454cf9f2f6b8df24a551bec0ecfdd74b

Modified Files
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doc/src/sgml/release-9.3.sgml | 712 ++++++++++++++++++++++++-----------------
1 file changed, 417 insertions(+), 295 deletions(-)

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