Bug about next_post_link and previous_post_link

There is a bug about next_post_link and previous_post_link.
These function can accept the third and the fourth arguments, but this plugin ignores them.
I think it should be fixed.

English reference about previous_post_link
http://codex.wordpress.org/Template_Tags/previous_post_link
Japanese reference about previous_post_link
http://wpdocs.sourceforge.jp/%E3%83%86%E3%83%B3%E3%83%97%E3%83%AC%E3%83%BC%E3%83%88%E3%82%BF%E3%82%B0/previous_post_link

http://wordpress.org/plugins/intuitive-custom-post-order/