Sessions: fixed logout() destroying normal session (instead of elevated) if $level = USER_LEVEL_CHPREF. Possible very minor security concern: elevated sessions were not fully destroyed, so if a normal session is opened from the same IP, the elevated one may be reusable for 15 minutes.

# Used for testing mod_rewrite.
<IfModule mod_rewrite.c>
RewriteEngine on

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule (.*) install.php?do=modrewrite_test&str=$1
</IfModule>