libfetch: support OpenSSL

TLS_client_method is a LibreSSL extension.
SSLv23_client_method is generic, and doesn't mean SSL v2/v3 only.

libfetch/common.c

@@ -504,7 +504,7 @@ fetch_ssl(conn_t *conn, const struct url *URL, int verbose)
 
 	SSL_load_error_strings();
 
-	conn->ssl_meth = TLS_client_method();
+	conn->ssl_meth = SSLv23_client_method();
 	conn->ssl_ctx = SSL_CTX_new(conn->ssl_meth);
 	SSL_CTX_set_mode(conn->ssl_ctx, SSL_MODE_AUTO_RETRY);