Move samples of int16_t format to sample_t, that is of type double

This prepares the correction of all levels

src/common/main_common.c

@@ -27,6 +27,7 @@
 #include <unistd.h>
 #include <math.h>
 #include <termios.h>
+#include "sample.h"
 #include "main.h"
 #include "debug.h"
 #include "sender.h"