pgsql: Merge visibility map crash-safety into index-only scan release n

Merge visibility map crash-safety into index-only scan release note
item, per Robert Haas.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/5428ff4af84e488c7f0629108cd12ff51125e09f

Modified Files
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doc/src/sgml/release-9.2.sgml | 16 +++-------------
1 files changed, 3 insertions(+), 13 deletions(-)