renderer: change frame_signal emission to pass previous_damage as data argument

This will make possible to users that are listening to frame_signal to get
previous_damage from the data parameter instead of using
output->previous_damage.

Signed-off-by: Leandro Ribeiro <leandrohr@riseup.net>

libweston/compositor.c

@@ -2723,7 +2723,7 @@ weston_output_repaint(struct weston_output *output, void *repaint_data)
 		weston_output_update_matrix(output);
 
 	r = output->repaint(output, &output_damage, repaint_data);
-	wl_signal_emit(&output->frame_signal, output);
+	wl_signal_emit(&output->frame_signal, &output_damage);
 
 	pixman_region32_fini(&output_damage);