Bugfix in LSA origination for PTP OSPF links.

Bugfix in LSA origination for PTP OSPF links.

The code generating LSAs for PTP OSPF links is buggy. The old behavior
is that it generates PTP link if there is a full/ptp neighbor and stub
link if there isn't. According to RFC 2328, the correct behavior is to
generate stub link in both cases (in the first case together with PTP
link).

And because of buggy detection of unnumbered networks, for numbered
networks the code creates stub links with 0.0.0.0/32.