Changed my mind about the EOF policy in SSH mode: I think the SSH

Changed my mind about the EOF policy in SSH mode: I think the SSH
backend should unilaterally assume outgoing EOF when it sees incoming
EOF, if and only if the main session channel is talking to a pty.
(Because ptys don't have a strong concept of EOF in the first place,
that seems like a sensible place to draw the line.) This fixes a bug
introduced by today's revamp in which if you used Unix Plink to run a
console session it would hang after you hit ^D - because the server
had sent EOF, but it was waiting for a client-side EOF too.

git-svn-id: svn://svn.tartarus.org/sgt/putty@9282 cda61777-01e9-0310-a592-d414129be87e