Make linum.el obsolete

* lisp/obsolete/linum.el: Add Obsolete-since.
* etc/NEWS: Announce obsoletion of linum.el.  (Bug#57412)

* doc/misc/efaq.texi (Displaying the current line or column):
* etc/TODO:
* lisp/faces.el: Don't mention linum.el.

doc/misc/efaq.texi

@@ -1810,9 +1810,6 @@ optional display.  Alternatively, you can use the
 customize @code{display-line-numbers-type} with the same value as you
 would use with @code{display-line-numbers}.
 
-There is also the @samp{linum} package which will henceforth become
-obsolete.  We recommend using @samp{display-line-numbers} instead.
-
 @node Displaying the current file name in the titlebar
 @section How can I modify the titlebar to contain the current file name?
 @cindex Titlebar, displaying the current file name in

etc/NEWS

@@ -389,6 +389,12 @@ The user options 'url-gateway-rlogin-host',
 'url-gateway-rlogin-parameters', and 'url-gateway-rlogin-user-name'
 are also obsolete.
 
+---
+** The linum.el library is now obsolete.
+We recommend using either the built-in `display-line-numbers-mode', or
+the `nlinum' package from GNU ELPA instead.  The former has better
+performance, but the latter is closer to a drop-in replacement.
+
 ---
 ** The autoarg.el library is now marked obsolete.
 This library provides the 'autoarg-mode' and 'autoarg-kp-mode' minor

etc/TODO

@@ -1686,12 +1686,6 @@ and the one to use when terminating the selection.
 More specifically do what's needed to make ibuffer.el the default, or
 just an extension of buff-menu.el.
 
-** Replace linum.el with nlinum.el
-https://lists.gnu.org/r/emacs-devel/2013-08/msg00379.html
-
-(Since Emacs 26 introduced native line numbers, this item is
-probably obsolete.)
-
 ** Merge sendmail.el and messages.el
 Probably not a complete merge, but at least arrange for messages.el to
 be a derived mode of sendmail.el.  Or arrange for messages.el to be

lisp/faces.el

@@ -2548,7 +2548,6 @@ default."
   :version "21.1"
   :group 'basic-faces)
 
-;; Definition stolen from linum.el.
 (defface line-number
   '((t :inherit (shadow default)))
   "Face for displaying line numbers.

lisp/obsolete/linum.el

@@ -6,6 +6,7 @@
 ;; Maintainer: emacs-devel@gnu.org
 ;; Keywords: convenience
 ;; Old-Version: 0.9x
+;; Obsolete-since: 29.1
 
 ;; This file is part of GNU Emacs.
 
@@ -24,6 +25,13 @@
 
 ;;; Commentary:
 
+;; NOTE: This library was made obsolete in Emacs 29.1.  We recommend
+;; using either the built-in `display-line-numbers-mode', or the
+;; `nlinum' package from GNU ELPA instead.  The former has better
+;; performance, but the latter is closer to a drop-in replacement.
+;;
+;; --------------------
+;;
 ;; Display line numbers for the current buffer.
 ;;
 ;; Toggle display of line numbers with M-x linum-mode.  To enable