Add support for the TLS Channel ID extension.

See http://tools.ietf.org/html/draft-balfanz-tls-channelid-00.

Change-Id: Id5b9799f96c0f7a1ef5ed8db9e40111a700d091f
diff --git a/ssl/s3_both.c b/ssl/s3_both.c
index af271d6..3a5b497 100644
--- a/ssl/s3_both.c
+++ b/ssl/s3_both.c
@@ -551,7 +551,8 @@
 		ssl3_take_mac(s);
 #endif
 	/* Feed this message into MAC computation. */
-	ssl3_finish_mac(s, (unsigned char *)s->init_buf->data, s->init_num + 4);
+	if (*s->init_buf->data != SSL3_MT_ENCRYPTED_EXTENSIONS)
+		ssl3_finish_mac(s, (unsigned char *)s->init_buf->data, s->init_num + 4);
 	if (s->msg_callback)
 		s->msg_callback(0, s->version, SSL3_RT_HANDSHAKE, s->init_buf->data, (size_t)s->init_num + 4, s, s->msg_callback_arg);
 	*ok=1;