Replace custom bool definitions with stdbool.h to work with C23.

--- a/lib/util/include/bool.h
+++ b/lib/util/include/bool.h
@@ -9,10 +9,7 @@
 /* At least the GNU compiler defines __bool_true_false_are_defined */
 #ifndef __bool_true_false_are_defined
 #define __bool_true_false_are_defined
-typedef enum {
-    false = 0,
-    true = 1
-} bool;
+#include <stdbool.h>
 #endif
 #endif