New field for user: autosubscribe

This sets the default value for on-the-fly forum subscription.
Defaults to on = subscribe.

(Also fixed a bug in postgres7.sql - a missing field for htmleditor!)

lib/db/postgres7.sql

@@ -126,6 +126,8 @@ CREATE TABLE prefix_user (
    description text,
    mailformat integer NOT NULL default '1',
    maildisplay integer NOT NULL default '2',
+   htmleditor integer NOT NULL default '1',
+   autosubscribe integer NOT NULL default '1',
    timemodified integer NOT NULL default '0',
    CONSTRAINT user_username_uk UNIQUE (username)
 );