Clean up header includes

- Remove <errno.h> because related functions are in util.c now
 - Remove corresponding <string.h> if not used otherwise

components/swap.c

@@ -1,5 +1,4 @@
 /* See LICENSE file for copyright and license details. */
-#include <errno.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>