Fixed a large client side memory leak for app_server memory.

* The areas allocated for BBitmaps were never deleted, even though the
  app_server deleted its part when the memory got freed.
* This resulted in a constant memory increase if the application in question
  would operate on many changing large bitmaps, like photos.
* Since the bitmaps are reference counted, we don't actually know when to delete
  the areas, so that the app_server now notifies the client whenever that is
  possible.
* This might fix #6824.

headers/private/app/ServerProtocol.h

@@ -1,5 +1,5 @@
 /*
- * Copyright 2001-2010, Haiku.
+ * Copyright 2001-2012, Haiku.
  * Distributed under the terms of the MIT License.
  *
  * Authors:
@@ -344,6 +344,12 @@ enum {
 	AS_LAST_CODE
 };
 
+// TODO: move this into a private app header, together with the rest of the
+//		private message definitions in AppDefs.h
+enum {
+	kMsgDeleteServerMemoryArea		= '_DSA',
+};
+
 // bitmap allocation flags
 enum {
 	kAllocator			= 0x1,