Make one last copy-editing pass over the 9.2 release notes.
Make one last copy-editing pass over the 9.2 release notes.

Also, set the release date to 2012-09-10, since we're pretty well
committed to that now.

arcivanov/postgres-xl,postmind-net/postgres-xl,arcivanov/postgres-xl,arcivanov/postgres-xl,snaga/postgres-xl,snaga/postgres-xl,postmind-net/postgres-xl,arcivanov/postgres-xl,postmind-net/postgres-xl,kmjungersen/PostgresXL,arcivanov/postgres-xl,snaga/postgres-xl,arcivanov/postgres-xl,postmind-net/postgres-xl,kmjungersen/PostgresXL,kmjungersen/PostgresXL,kmjungersen/PostgresXL,postmind-net/postgres-xl,kmjungersen/PostgresXL,snaga/postgres-xl,snaga/postgres-xl