* Change Makefile so release is the default mode, use DEBUG=1 to turn
on debugging.
* Clean up 'conf' a bit.
* Add a new option 'router' (valid in 'proxy' section) to turn on/off
the ND_NA_FLAG_ROUTER flag for adverts.
* Make iface::read() return a bit more generic address (sockaddr).
* Add is_unicast() and is_multicast() to address.
* Set default config path to "/etc/ndppd.conf".
* Silently ignore solicit messages with bad saddr and/or daddr.
- Clean up some junk code that was left over.
- Replace ptr<> with strong_ptr<> and weak_ptr<> to easier distinguish
between weak and strong pointers.
- Fix a couple of bugs.
