org-agenda: remove prefix-length property
* lisp/org-agenda.el (org-agenda-highlight-todo): Stop using prefix-length.
(org-cmp-alpha): Stop using prefix-length.
(org-agenda-open-link): Stop using prefix-length.
(org-agenda-change-all-lines): Stop using prefix-length.
* lisp/org-colview-xemacs.el (org-columns-display-here): Stop using
prefix-length. Always return claned items.
* lisp/org-colview.el (org-columns-display-here): Stop using
prefix-length. Always return claned items.
* lisp/org-mobile.el (org-mobile-write-agenda-for-mobile): Stop using
prefix-length.
Signed-off-by: Julien Danjou <julien@danjou.info>