pgsql: Update threading item: < Solaris) might benefit from

Log Message:
-----------
Update threading item:

< Solaris) might benefit from threading.

Solaris) might benefit from threading. Also explore the idea of
a single session using multiple threads to execute a query faster.

Modified Files:
--------------
pgsql/doc:
TODO (r1.1508 -> r1.1509)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/TODO.diff?r1=1.1508&amp;r2=1.1509)
pgsql/doc/src/FAQ:
TODO.html (r1.15 -> r1.16)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/FAQ/TODO.html.diff?r1=1.15&amp;r2=1.16)