[Bug libstdc++/77854] New: std::deque doesn't use allocator's size_type and difference_type

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77854

            Bug ID: 77854
           Summary: std::deque doesn't use allocator's size_type and
                    difference_type
           Product: gcc
           Version: 6.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org
  Target Milestone: ---

template<typename _Tp, typename _Alloc = std::allocator<_Tp> >
    class deque : protected _Deque_base<_Tp, _Alloc>
    {
      ...
      typedef size_t                             size_type;
      typedef ptrdiff_t                          difference_type;

These should come from allocator_traits