Prefer defvar-keymap and keymap-set in recentf.el
* lisp/recentf.el (recentf-mode-map): Prefer defvar-keymap. (recentf--shortcuts-keymap): Prefer keymap-set.
* lisp/recentf.el (recentf-mode-map): Prefer defvar-keymap. (recentf--shortcuts-keymap): Prefer keymap-set.