Standardised the culling flags between CullingSet and CullStack, and

made ENABLE_ALL_CULLING enable all culling including the near and far plane.
DEFAULT_CULLING is now used for the default as uses the same original
values as ENABLE_ALL_CULLING once did - view frustum culling with near and
far culling. SceneView now uses DEFAULT_CULLING.

src/osgUtil/SceneView.cpp

@@ -38,7 +38,7 @@ SceneView::SceneView(DisplaySettings* ds)
 
     _computeNearFar = CullVisitor::COMPUTE_NEAR_FAR_USING_BOUNDING_VOLUMES;
 
-    _cullingMode = osg::CullStack::ENABLE_ALL_CULLING;
+    _cullingMode = osg::CullStack::DEFAULT_CULLING;
     _LODScale = 1.0f;
     _smallFeatureCullingPixelSize = 3.0f;