Run in Linux

- Define Pi to avoid running into too many feature test macros
- Define _DEFAULT_SOURCE if not in OpenBSD
- Add a play target that works in Linux

Makefile

@@ -31,9 +31,15 @@ arngment: ${OBJ}
 
 ${OBJ}: ${HDR}
 
-play: all
+play:
+	@${MAKE} _play_$$(uname)
+
+_play_OpenBSD: all
 	./arngment ${ARNGMENT_ARGS} | aucat -e s16 -h raw -i -
 
+_play_Linux: all
+	./arngment ${ARNGMENT_ARGS} | aplay -f dat -t raw -
+
 clean:
 	rm -f arngment ${OBJ} ${P}-${V}.tgz