Add missing stdlib.h header to rsa sample programs
diff --git a/programs/pkey/rsa_encrypt.c b/programs/pkey/rsa_encrypt.c
index 1d35462..9154875 100644
--- a/programs/pkey/rsa_encrypt.c
+++ b/programs/pkey/rsa_encrypt.c
@@ -30,6 +30,7 @@
 #include "polarssl/platform.h"
 #else
 #include <stdio.h>
+#include <stdlib.h>
 #define polarssl_fprintf    fprintf
 #define polarssl_printf     printf
 #define polarssl_exit       exit