relay: Improve the comments on onionskin_answer()

  return 0;

}

/** Given a response payload and keys, initialize, then send a created

 * cell back.

/** On a relay, accept a create cell, initialise a circuit, and send a

 * created cell back.

 *

 * Given:

 *   - a response payload consisting of:

 *     - the <b>created_cell</b> and

 *     - an optional <b>rend_circ_nonce</b>, and

 *   - <b>keys</b> of length <b>keys_len</b>, which must be

 *     CPATH_KEY_MATERIAL_LEN;

 * then:

 *   - initialize the circuit <b>circ</b>'s cryptographic material,

 *   - set the circuit's state to open, and

 *   - send a created cell back on that circuit.

 *

 * If we haven't found our ORPorts reachable yet, and the channel meets the

 * necessary conditions, mark the relevant ORPorts as reachable.

 *

 * Returns -1 if cell or circuit initialisation fails.

 */

int

onionskin_answer(struct or_circuit_t *circ,