SceneCullingState with culling and camera frustum

- Fix for issue https://github.com/GarageGames/Torque3D/issues/525  This
fix takes into account the skewed view into the world when you have a
projection offset and the ability to see further into the scene at the
edges opposite to the offset.
- SceneCullingState now has two frustum rather than one: a culling
frustum and camera frustum.
- The camera frustum should be referenced when you need the projection
matrix or don't want a skewed frustum.
- The culling frustum should be referenced during any scene culling or
when determining what dynamic geometry to render.  It currently skews
itself to take into account any projection offset (automatically
calculated in SceneCullingState constructor).
- When there is no projection offset, the camera frustum and culling
frustum are the same.  This usually means any time when not using the
Oculus Rift.

Engine/source/scene/culling/sceneCullingState.h

@@ -100,9 +100,12 @@ class SceneCullingState
       /// The viewing state that defines how the scene is being viewed.
       SceneCameraState mCameraState;
 
-      /// The root culling volume corresponding to the camera frustum.
+      /// The root culling volume corresponding to the culling frustum.
       SceneCullingVolume mRootVolume;
 
+      /// The root culling frustum, which may be different from the camera frustum
+      Frustum mCullingFrustum;
+
       /// Occluders that have been added to this render state.  Adding an occluder does not
       /// necessarily result in an occluder volume being added.  To not repeatedly try to
       /// process the same occluder object, all objects that are added are recorded here.
@@ -136,7 +139,10 @@ class SceneCullingState
       SceneManager* getSceneManager() const { return mSceneManager; }
 
       /// Return the root frustum which is used to set up scene visibility.
-      const Frustum& getFrustum() const { return getCameraState().getFrustum(); }
+      const Frustum& getCullingFrustum() const { return mCullingFrustum; }
+
+      /// Return the root frustum which is used to set up scene visibility.
+      const Frustum& getCameraFrustum() const { return getCameraState().getFrustum(); }
 
       /// Return the viewing state that defines how the scene is being viewed.
       const SceneCameraState& getCameraState() const { return mCameraState; }