Segments a <list> in successives sublists which lengths are successive values of the list <segmentation>. <mode> indicates if <list> is to be read in a circular way. Ex. (group-list '(1 2 3 4) '(1 3) 'linear) => ((1) (2 3 4)) Ex. (group-list '(1 2 3 4) '(1 2 3) 'linear) => ((1) (2 3) (4)) Ex. (group-list '(1 2 3 4) '(1 2 3) 'circular) => ((1) (2 3) (4 1 2))