ECMP/multipath support

[Joakim Tjernlund]

> > > Other packets are sent to the neighbor IP address, which is a slight
> > > diversion from RFC 2328, but should not cause any problems.
> >
> > But a stricter router may reject OSPF msg over an ptp links if
> > they aren't addressed to AllSPFRouters.
>
> I just noticed you impl. a PTMP I/F type, nice :)

I updated to new nexhp calc. patch to match your latest
changes. I hope you like it.