* lisp/buff-menu.el: Convert to Tabulated List mode.

* lisp/buff-menu.el: Convert to Tabulated List mode.
(Buffer-menu-buffer+size-width): Make obsolete.
(Buffer-menu-name-width, Buffer-menu-size-width): New variables.
(Buffer-menu-mode-map): Inherit from tabulated-list-mode-map.
(Buffer-menu-mode): Derive from tabulated-list-mode.  Move command
documentation into docstring of buffer-menu.
(Buffer-menu-toggle-files-only): Add an informative message.
(Buffer-menu-sort): Convert to alias for tabulated-list-sort.
(Buffer-menu-buffer, Buffer-menu-beginning, Buffer-menu-mark)
(Buffer-menu-unmark, Buffer-menu-backup-unmark)
(Buffer-menu-delete, Buffer-menu-save, Buffer-menu-not-modified)
(Buffer-menu-execute, Buffer-menu-select)
(Buffer-menu-marked-buffers, Buffer-menu-toggle-read-only)
(Buffer-menu-bury): Use Tabulated List machinery.
(Buffer-menu-mouse-select, Buffer-menu-sort-by-column)
(Buffer-menu-sort-button-map, Buffer-menu-make-sort-button):
Deleted.
(list-buffers--refresh): New function.
(list-buffers-noselect): Use it.
(tabulated-list-entry-size->, Buffer-menu--pretty-name)
(Buffer-menu--pretty-file-name): New helper functions.

* lisp/loadup.el: Preload tabulated-list.

* lisp/emacs-lisp/tabulated-list.el (tabulated-list-sort): Rename from
tabulated-list-sort-column.
(tabulated-list-init-header): Add the initial aligning space even
if tabulated-list-padding is zero.

* src/lisp.mk (lisp): Update.