New command-line option in Plink (and PuTTY, though it's less useful

there): `plink host -nc host2:port' causes the SSH connection's main
channel to be replaced with a direct-tcpip connection to the
specified destination. This feature is mainly designed for use as a
local proxy: setting your local proxy command to `plink %proxyhost
-nc %host:%port' lets you tunnel SSH over SSH with a minimum of
fuss. Works on all platforms.

[originally from svn r6823]

putty.h

@@ -458,6 +458,8 @@ struct config_tag {
     int ssh_subsys;		       /* run a subsystem rather than a command */
     int ssh_subsys2;		       /* fallback to go with remote_cmd2 */
     int ssh_no_shell;		       /* avoid running a shell */
+    char ssh_nc_host[512];	       /* host to connect to in `nc' mode */
+    int ssh_nc_port;		       /* port to connect to in `nc' mode */
     /* Telnet options */
     char termtype[32];
     char termspeed[32];