Fixed texture optimization problem associated with mixing already compiled scene graphs - resulting

in incorrect texture assignment.  Solution was to a compareTextureObjects() test to the Texture*::compare(..) method that
the osgUtil::Optimizer::StateSetVisitor uses to determine uniqueness.

include/osg/Texture

@@ -599,6 +599,9 @@ class OSG_EXPORT Texture : public osg::StateAttribute
         /** Returns -1 if *this < *rhs, 0 if *this==*rhs, 1 if *this>*rhs. */
         int compareTexture(const Texture& rhs) const;
 
+        /** Returns -1 if *this < *rhs, 0 if *this==*rhs, 1 if *this>*rhs. */
+        int compareTextureObjects(const Texture& rhs) const;
+
         typedef buffered_value<unsigned int> TexParameterDirtyList;
         mutable TexParameterDirtyList _texParametersDirtyList;