pgsql: Add URLs for: * Consider compressing indexes by storing key

Log Message:
-----------
Add URLs for:

* Consider compressing indexes by storing key values duplicated in
several rows as a single index entry

http://archives.postgresql.org/pgsql-hackers/2006-12/msg00341.php
http://archives.postgresql.org/pgsql-hackers/2007-02/msg01264.php
http://archives.postgresql.org/pgsql-hackers/2007-03/msg00465.php

Modified Files:
--------------
pgsql/doc:
TODO (r1.2266 -> r1.2267)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/TODO?r1=1.2266&r2=1.2267)
pgsql/doc/src/FAQ:
TODO.html (r1.775 -> r1.776)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/FAQ/TODO.html?r1=1.775&r2=1.776)