Add #include <ctype.h> for the toupper macro/function

diff --git a/statusq.c b/statusq.c
index e8732e4b44706d35..ec34050dae2aeab0 100644
--- a/statusq.c
+++ b/statusq.c
@@ -31,6 +31,7 @@
 #include <string.h>
 #include <stdio.h>
 #include <stddef.h>
+#include <ctype.h>
 #include "errors.h"
 
 extern int quiet;