SSL_CTX_set_ecdh_auto deprecated.

[vlm]

SSL_CTX_set_ecdh_auto function is deprecated:

    if (ctx->config->ecdhecurve == -1) {
        SSL_CTX_set_ecdh_auto(*ssl_ctx, 1);
    } else if (ctx->config->ecdhecurve != NID_undef) {

It won't compile very soon. Need to make conditional compilation.

See https://github.com/openssl/openssl/issues/1437