Import macros IN_LINKLOCAL(), IN_PRIVATE(), IN_LOCAL_GROUP(), IN_ANY_LOCAL().
This is not a functional change.

IN_LINKLOCAL() tests if an address falls within the IPv4 link-local prefix.
IN_PRIVATE() tests if an address falls within an RFC 1918 private prefix.
IN_LOCAL_GROUP() tests if an address falls within the statically assigned
link-local multicast scope specified in RFC 2365.
IN_ANY_LOCAL() tests for either of IN_LINKLOCAL() or IN_LOCAL_GROUP().

As with the existing macros in the FreeBSD netinet stack, comparisons
are performed in host-byte order.