Rewrote osg:Statistics so that it is PrimitiveFunctor as is now completely

decoupled from osg::Drawable.  The Drawable::getStats() virtual method
no longer exists.

Updated the Viewer to use the osg::Statistics incarnation and reformated stats
to clean it up.

include/osgUtil/RenderBin

@@ -6,12 +6,14 @@
 #define OSGUTIL_RENDERBIN 1
 
 #include <osgUtil/RenderGraph>
-#include <osg/Statistics>
 
 #include <map>
 #include <vector>
 #include <string>
 
+// forward declare Statistics to remove link dependancy.
+namespace osg { class Statistics; }
+
 namespace osgUtil {
 
 class RenderStage;