Add a way to register loopers for quit

* BApplication can now take the job to quit a BLooper at
the application quit. It's rejecting requests from windows too.
* BMediaRoster is using now this service in conjunction with the
MediaRosterUndertaker.
* The BeBook specify that we should have a valid BApplication
before to instantiate the BMediaRoster. While in theory we should
add a debugger call when this situation happens, in pratice this
might lead to more problems. For example libraries might use the
media_kit and create a BApplication object, but they aren't
applications, this is a design problem. So I decided to replace it
with a TRACE call for the moment.

src/kits/app/Application.cpp

@@ -61,6 +61,7 @@ BMessenger be_app_messenger;
 
 pthread_once_t sAppResourcesInitOnce = PTHREAD_ONCE_INIT;
 BResources* BApplication::sAppResources = NULL;
+BObjectList<BLooper> sOnQuitLooperList;
 
 
 enum {
@@ -306,6 +307,13 @@ BApplication::~BApplication()
 	// tell all loopers(usually windows) to quit. Also, wait for them.
 	_QuitAllWindows(true);
 
+	// quit registered loopers
+	for (int32 i = 0; i < sOnQuitLooperList.CountItems(); i++) {
+		BLooper* looper = sOnQuitLooperList.ItemAt(i);
+		if (looper->Lock())
+			looper->Quit();
+	}
+
 	// unregister from the roster
 	BRoster::Private().RemoveApp(Team());
 
@@ -960,6 +968,40 @@ BApplication::LooperAt(int32 index) const
 }
 
 
+status_t
+BApplication::RegisterLooper(BLooper* looper)
+{
+	BWindow* window = dynamic_cast<BWindow*>(looper);
+	if (window != NULL)
+		return B_BAD_VALUE;
+
+	if (sOnQuitLooperList.HasItem(looper))
+		return B_ERROR;
+
+	if (sOnQuitLooperList.AddItem(looper) != true)
+		return B_ERROR;
+
+	return B_OK;
+}
+
+
+status_t
+BApplication::UnregisterLooper(BLooper* looper)
+{
+	BWindow* window = dynamic_cast<BWindow*>(looper);
+	if (window != NULL)
+		return B_BAD_VALUE;
+
+	if (!sOnQuitLooperList.HasItem(looper))
+		return B_ERROR;
+
+	if (sOnQuitLooperList.RemoveItem(looper) != true)
+		return B_ERROR;
+
+	return B_OK;
+}
+
+
 bool
 BApplication::IsLaunching() const
 {