pgsql: Clarify item: < * Consider use of open/fcntl(O_DIRECT) to

Log Message:
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Clarify item:

< * Consider use of open/fcntl(O_DIRECT) to minimize OS caching

* Consider use of open/fcntl(O_DIRECT) to minimize OS caching,
especially for WAL writes

Modified Files:
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pgsql/doc:
TODO (r1.1448 -> r1.1449)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/TODO.diff?r1=1.1448&amp;r2=1.1449)