pgsql: Use posix_fadvise() to avoid kernel caching of WAL contents on

Log Message:
-----------
Use posix_fadvise() to avoid kernel caching of WAL contents on WAL file
close.

ITAGAKI Takahiro

Modified Files:
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pgsql/src/backend/access/transam:
xlog.c (r1.237 -> r1.238)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/transam/xlog.c.diff?r1=1.237&r2=1.238)