mt.c: Include <sys/sysmacros.h> for minor()

We already do the same in stinit.c.

<sys/macros.h> is currently implicitly included by <sys/types.h>
but this might change in the future.

mt.c

@@ -21,6 +21,7 @@
 #include <sys/ioctl.h>
 #include <sys/stat.h>
 #include <sys/utsname.h>
+#include <sys/sysmacros.h>
 
 #include "mtio.h"
 #include "version.h"