Add the remote counterpart for the `local port forwardings accept

Add the remote counterpart for the `local port forwardings accept
connections from outside localhost' switch. Interestingly OpenSSH
3.0 appears to ignore this (though I know it works because ssh.com
3.0 gets it right, and the SSH packet dump agrees that I'm doing the
right thing).

git-svn-id: svn://svn.tartarus.org/sgt/putty@1496 cda61777-01e9-0310-a592-d414129be87e