SSL: server name callback changed to return SSL_TLSEXT_ERR_OK. OpenSSL 1.1.1 does not save server name to the session if server name callback returns anything but SSL_TLSEXT_ERR_OK, thus breaking the $ssl_server_name variable in resumed sessions. Since $ssl_server_name can be used even if we've selected the default server and there are no other servers, it looks like the only viable solution is to always return SSL_TLSEXT_ERR_OK regardless of the actual result. To fix things in the stream module as well, added a dummy server name callback which always returns SSL_TLSEXT_ERR_OK.

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