Add support for automatic ECDH temporary key parameter selection. When

enabled instead of requiring an application to hard code a (possibly
inappropriate) parameter set and delve into EC internals we just
automatically use the preferred curve.
(backport from HEAD)

ssl/ssl_cert.c

@@ -270,6 +270,7 @@ CERT *ssl_cert_dup(CERT *cert)
 			}
 		}
 	ret->ecdh_tmp_cb = cert->ecdh_tmp_cb;
+	ret->ecdh_tmp_auto = cert->ecdh_tmp_auto;
 #endif
 
 	for (i = 0; i < SSL_PKEY_NUM; i++)