unbound: avoid calling deprecated OpenSSL function

[emaste]

Summary

SSL_CTX_set_ecdh_auto is deprecated and has no effect (for reference see https://github.com/openssl/openssl/commit/2ecb9f2d18614fb7b7b42830a358b7163ed43221).

As unbound's config.h is manually maintained just turn off HAVE_DECL_SSL_CTX_SET_ECDH_AUTO so that it won't be called.

[ngie]

Sounds good to me! From https://www.openssl.org/docs/man3.1/man3/SSL_CTX_set_ecdh_auto.html :

SSL_CTX_set_ecdh_auto() and SSL_set_ecdh_auto() are deprecated and have no effect.

Oddly enough this function doesn't appear to be documented on 1.1..