Mantis #7567: added an 8-sec expiring item cache to the inventory network connector. This fixed the problem on my local test grid and generally made things faster. This cache has been needed for a while... there are many parts in the code where the sim gets an item multiple times in a short amount of time (rezzing attachs and objects, for example).

Other minor changes:
- added the scene as a parameter to the constructor od FetchInvDescHandler, so that I could see in which scene the handler was being called
- brought linked items in linked folders back to being prefetched

OpenSim/Region/ClientStack/Linden/Caps/WebFetchInvDescModule.cs

@@ -197,7 +197,7 @@ namespace OpenSim.Region.ClientStack.Linden
             m_LibraryService = Scene.LibraryService;
 
             // We'll reuse the same handler for all requests.
-            m_webFetchHandler = new FetchInvDescHandler(m_InventoryService, m_LibraryService);
+            m_webFetchHandler = new FetchInvDescHandler(m_InventoryService, m_LibraryService, Scene);
 
             Scene.EventManager.OnRegisterCaps += RegisterCaps;