clean up some tear-down

Windows continued to use function pointers belonging
to particular window ports that were still assigned
even after that port (tty) had gone through its
shutdown procedures when requested by the core.
Fix that and return to the minimal function pointers
that are not part of any of the actual WindowPorts.

sys/winnt/winnt.c

@@ -507,12 +507,13 @@ int code;
      * not vanish instantly after being created.
      * GUILaunched is defined and set in nttty.c.
      */
-    synch_cursor();
+
     if (GUILaunched)
-        getreturn("to end");
-    synch_cursor();
-    getreturn_enabled = TRUE;
-    wait_synch();
+        getreturn_enabled = TRUE;
+    else
+        windowprocs = *get_safe_procs(1);
+    if (getreturn_enabled)
+        wait_synch();
     exit(code);
 }