poly1305_finish
static inline void poly1305_finish(poly1305_context *ctx,
poly1305_finish(ctx, mac);
poly1305_finish((poly1305_state *)&ctx->poly, tag);
poly1305_finish(&poly1305_ctx, dst + src_len);
poly1305_finish(&poly1305_ctx, b.mac);
void poly1305_finish(poly1305_state *, unsigned char[16]);