pgsql: Add reliability docs about storage/memory corruptions.

pgsql: Add reliability docs about storage/memory corruptions.

Add reliability docs about storage/memory corruptions.
Add section to the Reliability section about what is and is not protected for
various file types.
Further edits welcome.

Designed to allow 1-2 line change when/if checksums are committed.

Inspired by docs written by Jeff Davis, though completely different from his
patch.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/2266db392cb825eccb39518e7b652e7f336fff6c

Modified Files
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doc/src/sgml/wal.sgml |   44 ++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 44 insertions(+), 0 deletions(-)