Make it possible to force all prims to be phantom via the collidable_prim boolean setting in the OpenSim.ini config [Startup] section.

Naturally, default is true.
When set to false, "phantom" flags on prims can be set as usual but all prims remain phantom.
This setting is for test purposes.
This switch does not affect the collision of avatars with the terrain.

OpenSim/Region/Framework/Scenes/SceneObjectPart.cs

@@ -1473,6 +1473,9 @@ namespace OpenSim.Region.Framework.Scenes
         /// <param name="VolumeDetectActive"></param>
         public void ApplyPhysics(uint rootObjectFlags, bool VolumeDetectActive)
         {
+            if (!ParentGroup.Scene.CollidablePrims)
+                return;
+
 //            m_log.DebugFormat(
 //                "[SCENE OBJECT PART]: Applying physics to {0} {1}, m_physicalPrim {2}",
 //                Name, LocalId, UUID, m_physicalPrim);
@@ -4318,7 +4321,7 @@ namespace OpenSim.Region.Framework.Scenes
                 if (ParentGroup.Scene == null)
                     return;
 
-                if (PhysActor == null)
+                if (ParentGroup.Scene.CollidablePrims && PhysActor == null)
                 {
                     // It's not phantom anymore. So make sure the physics engine get's knowledge of it
                     PhysActor = ParentGroup.Scene.PhysicsScene.AddPrimShape(