Fix the prototype of the stub function in noshare.c.

It's an old prototype from part way through the development of
connection sharing, which I must have forgotten to fix because by the
time I changed the prototype no platform was using noshare.c any more.

[originally from svn r10183]

noshare.c

@@ -14,7 +14,8 @@
 
 int platform_ssh_share(const char *name, Conf *conf,
                        Plug downplug, Plug upplug, Socket *sock,
-                       char **logtext)
+                       char **logtext, char **ds_err, char **us_err,
+                       int can_upstream, int can_downstream)
 {
     return SHARE_NONE;
 }