[sldev] New Inventory system patch

[Jason Giglio]

Hello,

I have just uploaded my inventory system patch to VWR-326. See below for 
changelog.

You can get the patch from:
https://jira.secondlife.com/browse/VWR-326

This patch:

1. Implements VWR-326 by adding a "5 items in 10 seconds" throttle.
	Throttled items are still accepted, just not displayed.
	This prevents the DoS attack described in VWR-326.

2. Adds a debug menu toggle to disable auto-opening of new inventory 
completely. This menu option persists between sessions.

3. Refactors the way new inventory items are opened/highlighted to 
remove the old hacky way.

4. Fixes a leaking observer in the inventory system related to 3

5. Fixes a rare crash by removing a null pointer dereference.