basic: include only what we use

This is a cleaned up result of running iwyu but without forward
declarations on src/basic.

src/basic/utf8.c

@@ -44,15 +44,14 @@
  */
 
 #include <errno.h>
-#include <inttypes.h>
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
 
 #include "alloc-util.h"
 #include "hexdecoct.h"
+#include "macro.h"
 #include "utf8.h"
-#include "util.h"
 
 bool unichar_is_valid(uint32_t ch) {