pgsql: Add: < * Reuse index tuples that point to rows that are not

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

< * Reuse index tuples that point to rows that are not visible to anyone?

* Reuse index tuples that point to heap tuples that are not visible to
anyone?

Modified Files:
--------------
pgsql/doc:
TODO (r1.1898 -> r1.1899)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/TODO.diff?r1=1.1898&amp;r2=1.1899)
pgsql/doc/src/FAQ:
TODO.html (r1.401 -> r1.402)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/FAQ/TODO.html.diff?r1=1.401&amp;r2=1.402)