Method set_len

Source/external/fast_float.h:1891–1893

set the length, without bounds checking.

  // set the length, without bounds checking.
  FASTFLOAT_CONSTEXPR14 void set_len(size_t len) noexcept {
	length = uint16_t(len);
  }
  constexpr size_t len() const noexcept {
	return length;
  }