pgsql: Add "AS" item: < * All backends running as threads in a single

Log Message:
-----------
Add "AS" item:

< * All backends running as threads in a single process (not want)

* All backends running as threads in a single process (not wanted)

< * Optimizer hints (not want)

* Optimizer hints (not wanted)

* Allow AS in "SELECT col AS label" to be optional (not wanted)

Because we support postfix operators, it isn't possible to make AS
optional and continue to use bison.
http://archives.postgresql.org/pgsql-sql/2006-08/msg00164.php

Modified Files:
--------------
pgsql/doc:
TODO (r1.1956 -> r1.1957)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/TODO.diff?r1=1.1956&amp;r2=1.1957)
pgsql/doc/src/FAQ:
TODO.html (r1.458 -> r1.459)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/FAQ/TODO.html.diff?r1=1.458&amp;r2=1.459)