[mod_mbedtls] include mbedtls/platform_util.h
include mbedtls/platform_util.h for mbedtls_platform_zeroize()
(instead of relying on an indirect include)
(fixes build with (very old) mbedtls-2.14.0)
#include <mbedtls/x509.h>
#include <mbedtls/x509_crt.h>
#include <mbedtls/version.h>
+#include <mbedtls/platform_util.h> /* mbedtls_platform_zeroize() */
#if MBEDTLS_VERSION_NUMBER >= 0x02040000 /* mbedtls 2.04.0 */
#include <mbedtls/net_sockets.h>
