Cygwin: pty: Stop counting number of slaves attached to pseudo console.

- The number of slaves attached to pseudo console is used only for
  triggering redraw screen. Counting was not only needless, but also
  did not work as expected. This patch removes the code for counting.

winsup/cygwin/fhandler_tty.cc

@@ -1019,8 +1019,6 @@ fhandler_pty_slave::close ()
   fhandler_pty_common::close ();
   if (!ForceCloseHandle (output_mutex))
     termios_printf ("CloseHandle (output_mutex<%p>), %E", output_mutex);
-  if (pcon_attached_to == get_minor ())
-    get_ttyp ()->num_pcon_attached_slaves --;
   return 0;
 }
 
@@ -2924,21 +2922,11 @@ fhandler_pty_slave::fixup_after_attach (bool native_maybe, int fd_set)
     {
       if (fhandler_console::get_console_process_id (get_helper_process_id (),
 						    true))
-	{
-	  if (pcon_attached_to != get_minor ())
-	    {
-	      pcon_attached_to = get_minor ();
-	      init_console_handler (true);
-	    }
-	  /* Clear screen to synchronize pseudo console screen buffer
-	     with real terminal. This is necessary because pseudo
-	     console screen buffer is empty at start. */
-	  if (get_ttyp ()->num_pcon_attached_slaves == 0)
-	    /* Assume this is the first process using this pty slave. */
-	    get_ttyp ()->need_redraw_screen = true;
-
-	  get_ttyp ()->num_pcon_attached_slaves ++;
-	}
+	if (pcon_attached_to != get_minor ())
+	  {
+	    pcon_attached_to = get_minor ();
+	    init_console_handler (true);
+	  }
 
 #if 0 /* This is for debug only. */
       isHybrid = true;

winsup/cygwin/tty.cc

@@ -242,9 +242,8 @@ tty::init ()
   screen_alternated = false;
   mask_switch_to_pcon_in = false;
   pcon_pid = 0;
-  num_pcon_attached_slaves = 0;
   term_code_page = 0;
-  need_redraw_screen = false;
+  need_redraw_screen = true;
   fwd_done = NULL;
   pcon_last_time = 0;
   pcon_in_empty = true;

winsup/cygwin/tty.h

@@ -103,7 +103,6 @@ private:
   bool screen_alternated;
   bool mask_switch_to_pcon_in;
   pid_t pcon_pid;
-  int num_pcon_attached_slaves;
   UINT term_code_page;
   bool need_redraw_screen;
   HANDLE fwd_done;