basic: include only what we use

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

src/basic/in-addr-util.c

@@ -20,9 +20,15 @@
 ***/
 
 #include <arpa/inet.h>
+#include <endian.h>
+#include <errno.h>
+#include <stdint.h>
+#include <stdlib.h>
 
 #include "alloc-util.h"
 #include "in-addr-util.h"
+#include "macro.h"
+#include "util.h"
 
 int in_addr_is_null(int family, const union in_addr_union *u) {
         assert(u);