Add accessors to config DN hints for cert request

mbedtls_ssl_conf_dn_hints()
mbedtls_ssl_set_hs_dn_hints()

Signed-off-by: Glenn Strauss <gstrauss@gluelogic.com>
diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index 119826f..8230163 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -850,6 +850,9 @@
 #if defined(MBEDTLS_SSL_SERVER_NAME_INDICATION)
     const unsigned char *sni_name;      /*!< raw SNI                        */
     size_t sni_name_len;                /*!< raw SNI len                    */
+#if defined(MBEDTLS_KEY_EXCHANGE_CERT_REQ_ALLOWED_ENABLED)
+    const mbedtls_x509_crt *dn_hints;   /*!< acceptable client cert issuers */
+#endif
 #endif /* MBEDTLS_SSL_SERVER_NAME_INDICATION */
 };