class SRefCountedNV

 A reference-counted stone without virtual functions, all functions inline.
 Note that the ref-count is not serialized -- so rebuild it in
 post-streaming function when necessary.
 As there are no virtual functions
   Int_t DecRefCount(Int_t rc=1);
 *must* be implmented in the sub-class. Macro
   SRefCountedNV_DecRefCount_macro
 is defined for this purpose in the header file. This implementation
 destructs the object when zero ref count is reached.