Method fixed_buffer_traits

include/fmt/base.h:1864–1864

 public:
  constexpr explicit fixed_buffer_traits(size_t limit) : limit_(limit) {}
  constexpr auto count() const -> size_t { return count_; }
  FMT_CONSTEXPR auto limit(size_t size) -> size_t {
    size_t n = limit_ > count_ ? limit_ - count_ : 0;