Update references to the padding draft.

The padding draft is now RFC 7685:
https://www.rfc-editor.org/rfc/rfc7685.txt

Change-Id: I26945b10e7923e75c016232c663baac11c4389ae

include/openssl/tls1.h

@@ -216,10 +216,7 @@ extern "C" {
 /* ExtensionType value from RFC7301 */
 #define TLSEXT_TYPE_application_layer_protocol_negotiation 16
 
-/* ExtensionType value for TLS padding extension.
- * http://www.iana.org/assignments/tls-extensiontype-values/tls-extensiontype-values.xhtml
- * http://tools.ietf.org/html/draft-agl-tls-padding-03
- */
+/* ExtensionType value from RFC7685 */
 #define TLSEXT_TYPE_padding 21
 
 /* https://tools.ietf.org/html/draft-ietf-tls-session-hash-01 */

ssl/t1_lib.c

@@ -2271,8 +2271,7 @@ int ssl_add_clienthello_tlsext(SSL *ssl, CBB *out, size_t header_len) {
   if (!SSL_IS_DTLS(ssl)) {
     header_len += CBB_len(&extensions) - orig_len;
     if (header_len > 0xff && header_len < 0x200) {
-      /* Add padding to workaround bugs in F5 terminators. See
-       * https://tools.ietf.org/html/draft-agl-tls-padding-03
+      /* Add padding to workaround bugs in F5 terminators. See RFC 7685.
        *
        * NB: because this code works out the length of all existing extensions
        * it MUST always appear last. */