When an ODE geom is removed (as when a non-phantom prim is deleted, resized or shape changed, also remove the OdeScene.actor_name_map entry pointing to the phys actor

This is to stop a small memory leak over time when prims are deleted or phantom-toggled

OpenSim/Region/Physics/OdePlugin/ODEPrim.cs

@@ -1448,6 +1448,7 @@ Console.WriteLine("CreateGeom:");
             {
                 try
                 {
+                    _parent_scene.actor_name_map.Remove(prim_geom);
                     d.GeomDestroy(prim_geom);
                     prim_geom = IntPtr.Zero;
                 }
@@ -1455,6 +1456,7 @@ Console.WriteLine("CreateGeom:");
                 {
                     prim_geom = IntPtr.Zero;
                     m_log.ErrorFormat("[PHYSICS]: PrimGeom dead for {0}", Name);
+
                     return false;
                 }