olm_pk_decrypt
external fun olm_pk_decrypt(decryption: OlmPkDecryptionPointer?, ephemeral_key: Pointer?, ephemeral_key_length: NativeSize, mac: Pointer?, mac_length: NativeSize, cipherText: Pointer?, cipherText_length: NativeSize, plaintext: Pointer?, max_plaintext_length: NativeSize): NativeSize