At present a get-scopes call returns a concrete array of dies, corresponding to
the long[] array returned by the underlying dwfl.

Instead encapsulate the long[] array in a DwarfScopeDies object and then only
create individual dies as needed - this should better match the underlying
interface where the dies array are just passed back to later functions - treated
like a handle.

It may even be possible to avoid the allocation of the long[] array, and just
encapsulate the malloc-ed pointer