pgsql: Add: > * Allow one transaction to see tuples using the snapshot

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

* Allow one transaction to see tuples using the snapshot of another
transaction

This would assist multiple backends in working together.
http://archives.postgresql.org/pgsql-hackers/2008-01/msg00400.php

Modified Files:
--------------
pgsql/doc:
TODO (r1.2402 -> r1.2403)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/TODO?r1=1.2402&r2=1.2403)
pgsql/doc/src/FAQ:
TODO.html (r1.908 -> r1.909)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/FAQ/TODO.html?r1=1.908&r2=1.909)