lib/calib.c: Include <sys/sysmacros.h> for fstat()

Relying on <sys/types.h> to define major(), minor() and makedev() is
deprecated, so include <sys/sysmacros.h> to define them.

Als include <sys/types.h> and <unistd.h> as the Linux man page for
fstat() has them in the synopsys.

lib/calib.c

@@ -27,7 +27,11 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
+#include <sys/types.h>
 #include <sys/stat.h>
+#include <sys/sysmacros.h>
+#include <unistd.h>
+
 #include "libinternal.h"
 
 static int set_calibration( comedi_t *dev, const comedi_calibration_t *parsed_file,