"Attached are updates of src/osg/Sequence.spp and include/osg/Sequence.
I've taken _sbegin/_send/_ubegin/_uend and _step our of the include file
and made them local variables in whatever method might need them.
I got rid of the _recalculate method as it was only getting used in
one place.
I also found a cut/paste bug in setMode's START case."
Note from Robert Osfield, Also includes some guards against crashes that was occuring in this new
code when handling empty Sequences.