fix various compiler warnings
diff --git a/src/qxdm-log.c b/src/qxdm-log.c
index 238417b..0423092 100644
--- a/src/qxdm-log.c
+++ b/src/qxdm-log.c
@@ -12,6 +12,7 @@
 #include <errno.h>
 
 #include <osmocom/core/msgb.h>
+#include <osmocom/core/serial.h>
 
 #include "diag_io.h"
 #include "protocol.h"