Added osg::EarthSky node to the core osg library, and added support for it into

osgUtil::SceneView, osg::CullVisitor, osgPlugin/osg and updated the hangglide
demo to use the new earth sky node.

include/osg/NodeVisitor

@@ -15,6 +15,7 @@ class LOD;
 class Sequence;
 class Switch;
 class Impostor;
+class EarthSky;
 
 /** Visitor for type safe operations on osg::Node's.
     Based on GOF's Visitor pattern.*/ 
@@ -128,6 +129,7 @@ class SG_EXPORT NodeVisitor : public Referenced
         virtual void apply(Sequence& node)   { apply((Group&)node); }
         virtual void apply(LOD& node)        { apply((Group&)node); }
         virtual void apply(Impostor& node)   { apply((LOD&)node); }
+        virtual void apply(EarthSky& node)   { apply((Group&)node); }
 
     protected:
 

include/osgUtil/CullVisitor

@@ -10,6 +10,7 @@
 #include <osg/State>
 #include <osg/Camera>
 #include <osg/Impostor>
+#include <osg/EarthSky>
 #include <osg/Notify>
 
 #include <osgUtil/RenderGraph>
@@ -47,12 +48,19 @@ class OSGUTIL_EXPORT CullVisitor : public osg::NodeVisitor
         virtual void apply(osg::Transform& node);
         virtual void apply(osg::Switch& node);
         virtual void apply(osg::LOD& node);
+        virtual void apply(osg::EarthSky& node);
         virtual void apply(osg::Impostor& node);
 
-        void setCamera(const osg::Camera& camera);
 
+
+        void setCamera(const osg::Camera& camera);
         const osg::Camera* getCamera() const { return _camera.get(); }
 
+
+        void setEarthSky(const osg::EarthSky* earthSky) { _earthSky = earthSky; }
+        const osg::EarthSky* getEarthSky() const { return _earthSky.get(); }
+
+
         void setLODBias(const float bias) { _LODBias = bias; }
         const float getLODBias() const    { return _LODBias; }
         
@@ -279,6 +287,8 @@ class OSGUTIL_EXPORT CullVisitor : public osg::NodeVisitor
         float _calculated_zfar;
         
         osg::ref_ptr<const osg::Camera> _camera;
+        
+        osg::ref_ptr<const osg::EarthSky> _earthSky;
 
         TransparencySortMode _tsm;