Rm _CRT_SECURE_NO_DEPRECATE for programs

(Already in config.h.)
diff --git a/programs/pkey/mpi_demo.c b/programs/pkey/mpi_demo.c
index f393f1d..cc57f5f 100644
--- a/programs/pkey/mpi_demo.c
+++ b/programs/pkey/mpi_demo.c
@@ -23,13 +23,10 @@
  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef _CRT_SECURE_NO_DEPRECATE
-#define _CRT_SECURE_NO_DEPRECATE 1
-#endif
+#include "polarssl/config.h"
 
 #include <stdio.h>
 
-#include "polarssl/config.h"
 #include "polarssl/bignum.h"
 
 #if !defined(POLARSSL_BIGNUM_C) || !defined(POLARSSL_FS_IO)