Remove the dead KAME code that dealt with IPv4-mapped IPv6 addresses.

Remove the dead KAME code that dealt with IPv4-mapped IPv6 addresses.
Add a check for IPv4-mapped IPv6 destination addresses, like in the most
recent KAME code, for non-connected sockets.  This prevents packets from
reaching the wire through the default route, if a reject route
for ::ffff:0.0.0.0/96 isn't present.  ok claudio@