[OSPF] Assign router address when only unnumbered I/Fs?

[Joakim Tjernlund <[e-mail]>]

I got routers which only have unnumbered PtoP interfaces and I wonder
how to advertise a host route as described in RFC 2328:
[2]It is possible for all of a router's interfaces to be unnumbered
    point-to-point links.  In this case, an IP address must be assigned
    to the router.  This address will then be advertised in the router's
    router-LSA as a host route.

The first that comes to mind is to just assign an IP address/32 to
the loopback or dummy interface and start OSPF on that I/F. However, you
can only assign one area to that I/F. How have other people
solved this?
Ideally there would be a command that lets me assign a
IP address which will be advertised in all areas.

 Jocke