Updates NEWS file for 0.9.0 release.

Added default computeBound() implementation to osg::Drawable which uses
a PrimtiveFunctor to compute the bounding box in a generic way, that
will work for all Drawable subclasses that implement the accept(PrimitiveFunctor&).

src/osg/GeoSet.cpp

@@ -416,6 +416,7 @@ void GeoSet::computeNumVerts() const
 }
 
 
+// just use the base Drawable's PrimitiveFunctor based implementation.
 const bool GeoSet::computeBound() const
 {
     _bbox.init();