The "New Thread" button in /forum is no longer restricted to those with
forum write capability: if you lack it, we now send you to the login
page instead.  Without this, users without the capability to post are
left looking in through the window of a building without obvious doors.
This change pairs especially nicely with the self-registration feature,
but it doesn't require it, since /login also allows anonymous login,
which should be enabled for Fossil forums on sites where non-users are
expected to visit.