BWindow: Fix keyboard handling bug.

- In the case of certain messages that are dispatched from the
  app_server with multiple target tokens (i.e. due to an attached
  view that has a mouse or keyboard event mask set), we need to
  strip the focus flag from the message before passing it to the
  non-focus views. Fixes a bug observed via Clipdinger where the
  aforementioned circumstance would result in all keyboard shortcuts
  being invoked multiple times.

src/kits/interface/Window.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright 2001-2015 Haiku, Inc. All rights reserved
+ * Copyright 2001-2016 Haiku, Inc. All rights reserved
  * Distributed under the terms of the MIT License.
  *
  * Authors:
@@ -3446,6 +3446,10 @@ BWindow::_UnpackMessage(unpack_cookie& cookie, BMessage** _message,
 			continue;
 
 		*_message = new BMessage(*cookie.message);
+		// the secondary copies of the message should not be treated as focus
+		// messages, otherwise there will be unintended side effects, i.e.
+		// keyboard shortcuts getting processed multiple times.
+		(*_message)->RemoveName("_feed_focus");
 		*_target = target;
 		cookie.index++;
 		return true;