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/common/Makefile.am

@@ -6,6 +6,7 @@ libcommon_a_SOURCES = \
 	../common/debug.c \
 	../common/timer.c \
 	../common/sound_alsa.c \
+	../common/wave.c \
 	../common/goertzel.c \
 	../common/jitter.c \
 	../common/loss.c \