Remove UNUSED macro

Use variables named unused instead which is simpler

util.h

@@ -3,7 +3,5 @@ extern char buf[1024];
 
 #define LEN(x) (sizeof (x) / sizeof *(x))
 
-#define UNUSED(x) (void)x
-
 const char *bprintf(const char *fmt, ...);
 int pscanf(const char *path, const char *fmt, ...);