First attempt at a Unix port of Plink. Seems to basically work;

doesn't yet use the SSH agent, no way to specify arbitrary config
options, no manpage yet, couple of other fiddly things need doing,
but it makes SSH connections and doesn't fall over horribly so I say
it's a good start. Now to run it under valgrind...

git-svn-id: svn://svn.tartarus.org/sgt/putty@2165 cda61777-01e9-0310-a592-d414129be87e