-- v2: dplayx/tests: Test receiving ADDFORWARDREPLY. dplayx: Handle ADDFORWARDREPLY and return error. dplayx/tests: Test receiving REQUESTPLAYERREPLY with error result. dplayx: Check reply result in DP_MSG_SendRequestPlayerId(). dplayx: Use the documented reply layout in DP_MSG_SendRequestPlayerId(). dplayx: Free message header on error path in DP_MSG_SendRequestPlayerId().