pgsql: Add: > * Reduce checkpoint performance degredation by forcing

Log Message:
-----------
Add:

* Reduce checkpoint performance degredation by forcing data to disk
more evenly

http://archives.postgresql.org/pgsql-hackers/2006-12/msg00337.php
http://archives.postgresql.org/pgsql-hackers/2007-01/msg00079.php

Modified Files:
--------------
pgsql/doc:
TODO (r1.2067 -> r1.2068)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/TODO.diff?r1=1.2067&r2=1.2068)
pgsql/doc/src/FAQ:
TODO.html (r1.568 -> r1.569)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/FAQ/TODO.html.diff?r1=1.568&r2=1.569)