Log Message:
-----------
Add section on reliable operation, talking about caching and storage
subsystem reliability.
Modified Files:
--------------
pgsql/doc/src/sgml:
wal.sgml (r1.31 -> r1.32)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/wal.sgml.diff?r1=1.31&r2=1.32)