Fixes SSL sample apps for non-default configs

Fixes the SSL sample applications to build for the non-default configs
which don't build if MBEDTLS_PLATFORM_C isn't defined.

programs/ssl/ssl_server.c

@@ -29,6 +29,9 @@
 #include "mbedtls/platform.h"
 #else
 #include <stdio.h>
+#include <stdlib.h>
+#define mbedtls_time       time
+#define mbedtls_time_t     time_t 
 #define mbedtls_fprintf    fprintf
 #define mbedtls_printf     printf
 #endif