Restore the independent LocalID numbering for avatars. Fixes an issue where

it becomes impossible to cross back into a region you came from, or freeze
several seconds after region crossings.

OpenSim/Framework/IScene.cs

@@ -45,6 +45,7 @@ namespace OpenSim.Framework
     public interface IScene
     {
         RegionInfo RegionInfo { get; }
+        uint NextAvatarLocalId { get; }
         RegionStatus Region_Status { get; set; }
 
         ClientManager ClientManager { get; }