Added a AnimationPathCallback which can update both a MatrixTransform and a

PositionAttitudeTransform, removed the equivialnt callbacks once found in these
transform classes.

Changed the NodeCallback class so its derived from osg::Object instead of
osg::Referenced to allow it to be saved out in the .osg format.

Added support for Update and Cull callbacks into the .osg file format.

Added support for AnimationPathCallback into the .osg file format.

src/osg/AnimationPath.cpp

@@ -1,5 +1,6 @@
 #include <osg/AnimationPath>
-#include <osg/NodeVisitor>
+#include <osg/MatrixTransform>
+#include <osg/PositionAttitudeTransform>
 
 using namespace osg;
 
@@ -67,3 +68,43 @@ bool AnimationPath::getInterpolatedControlPoint(double time,ControlPoint& contro
     }
     return true;
 }
+
+
+void AnimationPathCallback::operator()(Node* node, NodeVisitor* nv)
+{
+    if (_animationPath.valid() && 
+        nv->getVisitorType()==NodeVisitor::UPDATE_VISITOR && 
+        nv->getFrameStamp())
+    {
+        double time = nv->getFrameStamp()->getReferenceTime();
+        if (_firstTime==0.0) _firstTime = time;
+        
+        _animationTime = ((time-_firstTime)-_timeOffset)*_timeMultiplier;
+        
+        node->accept(*this);
+        
+    }
+
+    // must call any nested node callbacks and continue subgraph traversal.
+    NodeCallback::traverse(node,nv);
+}
+
+void AnimationPathCallback::apply(MatrixTransform& mt)
+{
+    Matrix matrix;
+    if (_animationPath->getMatrix(_animationTime,matrix))
+    {
+        mt.setMatrix(matrix);
+    }
+}
+
+
+void AnimationPathCallback::apply(PositionAttitudeTransform& pat)
+{
+    AnimationPath::ControlPoint cp;
+    if (_animationPath->getInterpolatedControlPoint(_animationTime,cp))
+    {
+        pat.setPosition(cp._position);
+        pat.setAttitude(cp._rotation);
+    }
+}