pgsql: Add URL for: * Improve speed with indexes For large table

Log Message:
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Add URL for:

* Improve speed with indexes

For large table adjustments during VACUUM FULL, it is faster to cluster
or reindex rather than update the index. Also, index updates can bloat
the index.

Modified Files:
--------------
pgsql/doc:
TODO (r1.2191 -> r1.2192)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/TODO.diff?r1=1.2191&r2=1.2192)
pgsql/doc/src/FAQ:
TODO.html (r1.692 -> r1.693)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/FAQ/TODO.html.diff?r1=1.692&r2=1.693)