COMP: resolve label-size=64 ambiguities for clang

* DynList construction with integer parameter:

    DynList<T>(int32_t) - eg DynList<T> lst(10)

  Candidates are

     DynList(const label)
     template<class ListType> DynList(const ListType& lst)

  It picks the second as the beter match (error).

  Resolve by adding DynList(int32_t) constructor for label-size=64

* Similar problem with copy assignment.
     dyList = -1 (for example) picks
     template<class ListType> operator=(const ListType& lst)

  Resolve by replacing general list assignment with assignments for
  DynList, UList, FixedList