common code: Add feature to record received audio and replay it

-W <file.wav> writes a wave file of received audio
-R <file.wav> reads a wave file to feed into decoder

This way you can record a phone and later debug without a phone
and radio equipment.

src/nmt/main.c

@@ -235,7 +235,7 @@ int main(int argc, char *argv[])
 	}
 
 	/* create transceiver instance */
-	rc = nmt_create(sounddev, samplerate, kanal, (loopback) ? CHAN_TYPE_TEST : chan_type, ms_power, nmt_digits2value(traffic_area, 2), area_no, compander, supervisory, loopback);
+	rc = nmt_create(sounddev, samplerate, write_wave, read_wave, kanal, (loopback) ? CHAN_TYPE_TEST : chan_type, ms_power, nmt_digits2value(traffic_area, 2), area_no, compander, supervisory, loopback);
 	if (rc < 0) {
 		fprintf(stderr, "Failed to create transceiver instance. Quitting!\n");
 		goto fail;