Added basic code injection fields to osg::Shader,

creation of main shader to ShaderComposer and
collection of ShaderComponent to osg::State.
Also added very basic shader set up in osgshadecomposition example.

include/osg/State

@@ -142,6 +142,12 @@ class OSG_EXPORT State : public Referenced, public Observer
         inline unsigned int getContextID() const { return _contextID; }
 
 
+        /* Set whether shader composition is enabled.*/
+        void setShaderCompositionEnabled(bool flag) { _shaderCompositionEnabled = flag; }
+
+        /* Get whether shader composition is enabled.*/
+        bool getShaderCompositionEnabled() const { return _shaderCompositionEnabled; }
+
         /** Set the ShaderComposor object that implements shader composition.*/
         void setShaderComposer(ShaderComposer* sc) { _shaderComposer = sc; }
 
@@ -250,6 +256,8 @@ class OSG_EXPORT State : public Referenced, public Observer
          */
         void apply();
 
+        /** Apply any shader composed state.*/
+        void applyShaderComposition();
 
         /** Set whether a particular OpenGL mode is valid in the current graphics context.
           * Use to disable OpenGL modes that are not supported by current graphics drivers/context.*/