patch adding none cipher/mac for ssh v2

[Michael A Stevens]

> I didn't say I do need it. But I do understand J Raynor's explanation. J 
> wants to use ssh authentication without incurring crypto overhead on the 
> session; this saves CPU when doing large transfers. This is handy for scp or 
> rsync over ssh (I usually use blowfish for this since it seems to be the 
> fastest cipher in the suite). J specifically stated that this could be used 
> on channels that are already secure, e.g. IPsec or ssh tunnels.

The factest cipher from our tests has been arcfour, by a wide margin.