(and minor changes in documentation)

Sending malformed network prefixes in LSAs causes OSPF to crash
just after the LSA is propagated to the other routers.

Mainly changes IA_UNNUMBERED to IA_PEER and adds IA_HOST. Also do not
show broadcast addr in show interfaces. Nobody cares for that.

The old BIRD grammar needs two lookaheads to distinguish if..else from
else: in case, which caused the parser to fail on some combinations of
both expressions.

This patch replaces two tokens 'else' ':' by one token 'else:' to fix
that.

Now it can handle a change in iface pattern structure.
It can add, remove and reconfigure interfaces, vlinks and areas.

Thanks to Joakim Tjernlund for the idea.

And updates a comment.

Also changes some symbol names (IFF_ADMIN_DOWN -> IFF_SHUTDOWN,
IFF_LINK_UP -> IFF_ADMIN_UP).

We should be able to send everything we received.

Also add a new option 'dual' for the old behavior.