Implemented direct message passing for local targets; this fixes a deadlock

with PostMessage() in case the message queue is full.
Some notes:
* for synchronous replies, we don't use this mechanism yet, but it could be
  extended to do that as well.
* the code looks so complicated because we need a way to access the looper's
  queue without locking it (to prevent deadlocks); like Dano's solution, I've
  abused BTokenSpace to store a BDirectMessageTarget with a BHandler.
* we also need to decouple the lifetime of a looper's queue from its target,
  as we cannot lock the looper, and therefore, can't guarantee it stays valid
  as long as we're accessing it outside of BLooper.
* init_clipboard() now needs to be done after the global constructors have
  been called - since sending messages now needs gDefaultTokens to be initialized.
  Since this is done per image, it shouldn't cause any troubles, though.
* some minor cleanup, removed unused _msg_cache_cleanup_() and friends.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@19968 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/kits/interface/Window.cpp

@@ -25,6 +25,7 @@
 #include <input_globals.h>
 #include <AppMisc.h>
 #include <ApplicationPrivate.h>
+#include <DirectMessageTarget.h>
 #include <InputServerTypes.h>
 #include <MenuPrivate.h>
 #include <MessagePrivate.h>
@@ -2488,7 +2489,7 @@ BWindow::_DequeueAll()
 	for (int32 i = 0; i < count; i++) {
 		BMessage *message = MessageFromPort(0);
 		if (message != NULL)
-			fQueue->AddMessage(message);
+			fDirectTarget->Queue()->AddMessage(message);
 	}
 }
 
@@ -2536,8 +2537,8 @@ BWindow::task_looper()
 
 		bool dispatchNextMessage = true;
 		while (!fTerminating && dispatchNextMessage) {
-			//	Get next message from queue (assign to fLastMessage)
-			fLastMessage = fQueue->NextMessage();
+			// Get next message from queue (assign to fLastMessage)
+			fLastMessage = fDirectTarget->Queue()->NextMessage();
 
 			// Lock the looper
 			if (!Lock())