* org-list.el (org-list-separating-blank-lines-number): use new
accessors.
(org-list-insert-item-generic): use list structures to insert a new
item.
(org-list-exchange-items): refactor and comment code. Now return new
struct instead of modifying it, as list sorting would sometimes eat
first item.
(org-move-item-down,org-move-item-up): reflect changes to
`org-list-exchange-items'.
(org-insert-item): as `org-in-item-p' also computes item beginning
when applicable, reuse the result.
* org-timer.el (org-timer-item): as `org-in-item-p' also computes item
beginning when applicable, reuse the result.