Function to_pointer

include/fmt/format.h:502–504

template <typename T, typename OutputIt>
constexpr auto to_pointer(OutputIt, size_t) -> T* {
  return nullptr;
}
template <typename T> FMT_CONSTEXPR auto to_pointer(T*& ptr, size_t n) -> T* {
  T* begin = ptr;
  ptr += n;