pgsql: Add: > * Allow UPDATEs on only non-referential integrity columns

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

* Allow UPDATEs on only non-referential integrity columns not to conflict
with referential integrity locks

http://archives.postgresql.org/pgsql-hackers/2007-02/msg00073.php

Modified Files:
--------------
pgsql/doc:
TODO (r1.2103 -> r1.2104)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/TODO.diff?r1=1.2103&r2=1.2104)
pgsql/doc/src/FAQ:
TODO.html (r1.604 -> r1.605)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/FAQ/TODO.html.diff?r1=1.604&r2=1.605)