Add missing #include in netdb.c for atoi()

src/api/netdb.c

@@ -46,7 +46,8 @@
 #include "lwip/api.h"
 #include "lwip/dns.h"
 
-#include <string.h>
+#include <string.h> /* memset */
+#include <stdlib.h> /* atoi */
 
 /** helper struct for gethostbyname_r to access the char* buffer */
 struct gethostbyname_r_helper {