[patch] libstdc++/66742 use allocators correctly in list::sort()

[Jonathan Wakely]

On 03/07/15 18:56 +0200, Daniel Krügler wrote:
>- Isn't it necessary to cope with possibly final allocators when
>unconditionally forming the derived member class
>
>struct _Impl : allocator_type

If the allocator was final we couldn't even instantiate std::list
because of this in _List_base:

      struct _List_impl
      : public _Node_alloc_type
      {

This is https://gcc.gnu.org/PR60921 and I'm going to fix it
everywhere, so I'm not concerned about this one place yet.