message: optional #define to turn off default-approximate mode
diff: #define ENOKI_CHKSCALAR if (std::is_arithmetic<std::decay_t<Value>>::value) { ENOKI_TRACK_SCALAR }
  +#if !defined(ENOKI_APPROX_DEFAULT)
  +# define ENOKI_APPROX_DEFAULT 1
  +#endif
  +
  NAMESPACE_BEGIN(enoki)
  using ssize_t = std::make_signed_t<size_t>;
  @@ -251,7 +255,11 @@ using is_std_int =
  /// Value trait to determine if a type should be handled using approximate mode by default
  template <typename T, typename = int> struct approx_default {
  +#if ENOKI_APPROX_DEFAULT == 1
  static constexpr bool value = is_std_float<std::decay_t<T>>::value;
  +#else
  + static constexpr bool value = false;
  +#endif
  };
  NAMESPACE_END(detail)
  