genlist: Refactoring genlist codes.

genlist: Refactoring genlist codes.

<Comment by SeoZ>
	This is a partial commit of D788.
	As D788 is huge patch and genlist is really fragile, I decided to
	split this patch and it was partially done on the airplane during
	my business trip last month. As I had no solid amount of time to
	finish that job after that trip, I decided to push existing patches
	first. I will finish this job soon. Sorry bluezery.
	But I will keep your credit on the merge commit. Please make an
	atomic patch next time. You can do it.