Improvement suggestion for 6in4 docs.

[elf@florence.buici.com]

I've been working to get ipv6 running on one of my machines for a
couple of days.  The freenet6 ip tunnel allocation script appears to
have a hiccup where it sends me an address different from the one it
*really* assigns.  6in4 appears to be a more reliable config.

Yet it is difficult to reconcile the ipv6 setup page with the use of a
6in4 address.  What I finally did was add the following to my
interfaces file:

iface eth0 inet6 static
  address 2002:ce7c:8e1c::1:1
  netmask 48
  up ip link set sit0 up
  up ip addr add 2002:ce7c:8e1c::1 dev sit0
  up ip route add 2000::0/3 via ::131.107.152.32
  down ip link set sit0 down

My suggestion is that we make it a bit more clear about how to
configure using 6in4 versus a conventional v4tunnel...as long as this
is the best way to do it.

An example of the bind reverse lookup would be handy, too.  I think I
understand what is meant, but it would still be helpful to see an
example.

Cheers.