Add handshake hints for TLS 1.2 session tickets.

This runs through much the same code as the TLS 1.3 bits, though we use
a different hint field to avoid mixups between the fields. (Otherwise
the receiver may misinterpret a decryptPSK hint as the result of
decrypting the session_ticket extension, or vice versa. This could
happen if a ClientHello contains both a PSK and a session ticket.)

Bug: 504
Change-Id: I968bafe12120938e6e46e52536efd552b12c66a0
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/53805
Auto-Submit: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: Adam Langley <agl@google.com>
diff --git a/ssl/internal.h b/ssl/internal.h
index 0a15ace..153c9ca 100644
--- a/ssl/internal.h
+++ b/ssl/internal.h
@@ -1719,6 +1719,10 @@
   uint16_t ecdhe_group_id = 0;
   Array<uint8_t> ecdhe_public_key;
   Array<uint8_t> ecdhe_private_key;
+
+  Array<uint8_t> decrypted_ticket;
+  bool renew_ticket = false;
+  bool ignore_ticket = false;
 };
 
 struct SSL_HANDSHAKE {