[patch] add text in community/lists/

Hi,

I propose to add the note about unacceptable addresses in our subscribe
page, per the attached patch.  Please object if you think it's a bad
idea to mention the name of the system form layout in a comment in the
HTML file -- I'm open to better suggestions.  (Just removing the comment
does not seem a good idea however).

Note: I did not test it.

--
Alvaro Herrera                                http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support