Abstracts away time()/stdlib.h into platform

Substitutes time() into a configurable platform interface to allow it to be
easily substituted.

library/ssl_tls.c

@@ -35,6 +35,15 @@
 
 #if defined(MBEDTLS_SSL_TLS_C)
 
+#if defined(MBEDTLS_PLATFORM_C)
+#include "mbedtls/platform.h"
+#else
+#include <stdlib.h>
+#define mbedtls_calloc    calloc
+#define mbedtls_free      free
+#define mbedtls_time_t    time_t
+#endif
+
 #include "mbedtls/debug.h"
 #include "mbedtls/ssl.h"
 #include "mbedtls/ssl_internal.h"
@@ -46,14 +55,6 @@
 #include "mbedtls/oid.h"
 #endif
 
-#if defined(MBEDTLS_PLATFORM_C)
-#include "mbedtls/platform.h"
-#else
-#include <stdlib.h>
-#define mbedtls_calloc    calloc
-#define mbedtls_free       free
-#endif
-
 /* Implementation that should never be optimized out by the compiler */
 static void mbedtls_zeroize( void *v, size_t n ) {
     volatile unsigned char *p = v; while( n-- ) *p++ = 0;