Pass the message body to decrypt_max_plaintext_length so we can get a more accurate estimate, rename encrypt_max_output_length to encrypt_output_length and change the api to return the exact number of bytes needed to hold the message

git-subtree-dir: lib/ed25519
git-subtree-split: 1fc4a2ff69fe111875bd5efcc8523e40b18cf673

git-subtree-dir: lib/crypto-algorithms
git-subtree-split: 100f4ff91b5a5b31a84b3999365c3058df6251ea

git-subtree-dir: lib/curve25519-donna
git-subtree-split: 28772f37a4b8a57ab9439b9e79b19f9abee686da