Clean up header includes

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

components/uptime.c

@@ -29,8 +29,6 @@ format(int uptime)
 		return format(uptime);
 	}
 #elif defined(__OpenBSD__)
-	#include <errno.h>
-	#include <string.h>
 	#include <sys/sysctl.h>
 	#include <sys/time.h>