default AttributeDeleteFunctor which uses delete []. Users can create
their own handlers for the attribute memory to override this default
behavior.
Fixed a typo in ReaderWriterOBJ.cpp.
and have updated GeoSet to use mutable values for the _numverts etc, allowing
osg::GeoSet::computeNumVerts() to be a const operation. osg::GeoSet::getNumVerts
is now a const once more, so avoiding compilation problems. Also chaned the new
osgconv orientation code to use a Drawable::AttributeFunctor so it can work on
other Drawables other than just GeoSets.