RIP sockets for multiple ifaces collided, because we cannot bind to
a specific iface on BSD. Workarounded by SO_REUSEPORT.
Thanks to Eugene M. Zheganin for the bugreport.
- BSD kernel syncer is now self-conscious and can learn alien routes
- important bugfix in BSD kernel syncer (crash after protocol restart)
- many minor changes and bugfixes in kernel syncers and neighbor cache
- direct protocol does not generate host and link local routes
- min_scope check is removed, all routes have SCOPE_UNIVERSE by default
- also fixes some remaining compiler warnings
