Clean up header includes

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

components/num_files.c

@@ -1,6 +1,5 @@
 /* See LICENSE file for copyright and license details. */
 #include <dirent.h>
-#include <errno.h>
 #include <stdio.h>
 #include <string.h>