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_client1.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

programs/ssl/ssl_client2.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_printf     printf
 #define mbedtls_fprintf    fprintf
 #define mbedtls_snprintf   snprintf

programs/ssl/ssl_mail_client.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

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

programs/ssl/ssl_server2.c

@@ -29,7 +29,10 @@
 #include "mbedtls/platform.h"
 #else
 #include <stdio.h>
+#include <stdlib.h>
 #define mbedtls_free       free
+#define mbedtls_time       time
+#define mbedtls_time_t     time_t
 #define mbedtls_calloc    calloc
 #define mbedtls_fprintf    fprintf
 #define mbedtls_printf     printf

programs/test/udp_proxy.c

@@ -34,11 +34,15 @@
 #if defined(MBEDTLS_PLATFORM_C)
 #include "mbedtls/platform.h"
 #else
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#define mbedtls_time       time
+#define mbedtls_time_t     time_t
 #define mbedtls_printf     printf
 #endif
 
 #if !defined(MBEDTLS_NET_C)
-#include <stdio.h>
 int main( void )
 {
     mbedtls_printf( "MBEDTLS_NET_C not defined.\n" );
@@ -50,10 +54,7 @@ int main( void )
 #include "mbedtls/error.h"
 #include "mbedtls/ssl.h"
 
-#include <stdio.h>
-#include <stdlib.h>
 #include <string.h>
-#include <time.h>
 
 /* For select() */
 #if (defined(_WIN32) || defined(_WIN32_WCE)) && !defined(EFIX64) && \