use SNI when connecting with SSL

based on patch by Vincent Bernat <vincent@bernat.ch>.

src/socket.c

@@ -271,6 +271,8 @@ socket_start_tls( conn_t *conn, void (*cb)( int ok, void *aux ) )
 
 	init_wakeup( &conn->ssl_fake, ssl_fake_cb, conn );
 	conn->ssl = SSL_new( ((server_conf_t *)conn->conf)->SSLContext );
+	if (ssl_return( "set server name", conn, SSL_set_tlsext_host_name( conn->ssl, conn->conf->host ) ) < 0)
+		return;
 	SSL_set_fd( conn->ssl, conn->fd );
 	SSL_set_mode( conn->ssl, SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER );
 	socket_expect_read( conn, 1 );