Added support for sharing arrays in the .osg format for osg::Geometry.

Fixed the osgUtil::Optimizater so it takes into account sharing of arrays when
deciding whether an geometry can be merged or not.

include/osgUtil/Optimizer

@@ -188,6 +188,8 @@ class OSGUTIL_EXPORT Optimizer
 
                 static bool mergeGeode(osg::Geode& geode);
 
+                static bool geometryContainsSharedArrays(osg::Geometry& geom);
+
                 static bool mergeGeometry(osg::Geometry& lhs,osg::Geometry& rhs);
 
                 static bool mergePrimitive(osg::DrawArrays& lhs,osg::DrawArrays& rhs);