Addd libraryName() method to osg::Object in preperation for the osgDB support

for node kits plugins.

include/osgParticle/Interpolator

@@ -26,6 +26,7 @@ namespace osgParticle
         Interpolator(const Interpolator &copy, const osg::CopyOp &copyop = osg::CopyOp::SHALLOW_COPY)
         : osg::Object(copy, copyop) {}
         
+        virtual const char *libraryName() const { return "osgParticle"; }
         virtual const char *className() const { return "Interpolator"; }
         virtual bool isSameKindAs(const osg::Object *obj) const { return dynamic_cast<const Interpolator *>(obj) != 0; }