Fix for FAQ and/or man(1) ssh

Hello,

I think the ssh documentation on port forwarding is confusing in a
subtle way. It is precise but not accessible to many people, all to many
of whom seem to want to ask me :-)

At http://shearer.org/Ssh_tunnelling I have explained the problem,
written some words that could be extracted for the FAQ, and suggested an
improvement to the wording of -L for man(1) ssh.

I thought I'd handle this as a documentation comment rather than submit
a patch, because there isn't exactly a bug in the sense that the
existing documentation is completely correct.

Regards,

-- 
Dan Shearer
[email protected]