Check if batching for two elements is worth it

[drskalman]

        // TODO: Bentchmark these two variants
        // Variant 1.  Do not batch any normalizations
        let message = E::prepare_signature(message.hash_to_signature_curve::<E>());
        let signature = E::prepare_signature(self.0);
        // Variant 2.  Batch signature curve normalizations
        //   let mut s = [E::hash_to_signature_curve(message), signature.0];
        //   E::SignatureCurve::batch_normalization(&s);
        //   let message = s[0].into_affine().prepare();
        //   let signature = s[1].into_affine().prepare();
        // TODO: Compare benchmarks on variants