Added a ShadowTechniue::setShadowedScene() virtual method to make it possible to implement techniques as fascades to other techniques

include/osgShadow/ShadowTechnique

@@ -27,7 +27,7 @@ namespace osgShadow {
 // forward declare ShadowedScene
 class ShadowedScene;
 
-/** ShadowedScene provides a mechanism for decorating a scene that the needs to have shadows cast upon it.*/
+/** ShadowTechnique is the base class for different shadow implementations.*/
 class OSGSHADOW_EXPORT ShadowTechnique : public osg::Object
 {
     public :
@@ -39,6 +39,8 @@ class OSGSHADOW_EXPORT ShadowTechnique : public osg::Object
         virtual const char* libraryName() const { return "osgShadow"; }\
         virtual const char* className() const { return "ShadowTechnique"; }
 
+        virtual void setShadowedScene(ShadowedScene* ss);
+
         ShadowedScene* getShadowedScene() { return _shadowedScene; }
 
         const ShadowedScene* getShadowedScene() const { return _shadowedScene; }