Try to remove #include <stdlib.h> from many files. Does not seem necessary any more and might cause problems when porting lwIP.

src/apps/httpd/httpd.c

@@ -99,7 +99,6 @@
 #include "lwip/tcp.h"
 
 #include <string.h>
-#include <stdlib.h>
 #include <stdio.h>
 
 #if LWIP_TCP

src/apps/mdns/mdns.c

@@ -65,7 +65,6 @@
 #include "lwip/prot/dns.h"
 
 #include <string.h>
-#include <stdlib.h>
 
 #if LWIP_MDNS_RESPONDER