SSL_session_reused - query whether a reused session was negotiated during
  handshake
 #include <openssl/ssl.h>
 int SSL_session_reused(const SSL *ssl);
Query, whether a reused session was negotiated during the handshake.
During the negotiation, a client can propose to reuse a session. The server then
  looks up the session in its cache. If both client and server agree on the
  session, it will be reused and a flag is being set that can be queried by the
  application.
The following return values can occur:
  - 0
- A new session was negotiated.
- 1
- A session was reused.
ssl(7), SSL_set_session(3),
  SSL_CTX_set_session_cache_mode(3)
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    You may not use this file except in compliance with the License. You can
    obtain a copy in the file LICENSE in the source distribution or at
    <https://www.openssl.org/source/license.html>.