Make elint obsolete (bug#78685)

It never was very useful to begin with, produces lots of false positives,
and the byte-compiler has long eclipsed it in warning quality.

* lisp/emacs-lisp/elint.el: Move this file...
* lisp/obsolete/elint.el: ...here, and declare obsolete.
(elint-file, elint-directory, elint-current-buffer, elint-defun):
Declare obsolete.
(elint--file): Split from elint-file to avoid warning.
* lisp/progmodes/elisp-mode.el (emacs-lisp-mode-menu):
Remove elint menu entries.
* etc/NEWS: Announce

etc/NEWS

@@ -2318,6 +2318,10 @@ indicate problems in Org, and if found, will ask whether the bug report
 is actually about Org (in which case users should use the Org-specific
 command for reporting bugs).
 
+---
+** The elint package is now obsolete.
+Use the byte-compiler instead; it provides more and more useful warnings.
+
 
 
 * New Modes and Packages in Emacs 31.1

lisp/obsolete/elint.el

@@ -5,6 +5,7 @@
 ;; Author: Peter Liljenberg <petli@lysator.liu.se>
 ;; Maintainer: emacs-devel@gnu.org
 ;; Created: May 1997
+;; Obsolete-since: 31.1
 ;; Keywords: lisp
 
 ;; This file is part of GNU Emacs.
@@ -24,6 +25,8 @@
 
 ;;; Commentary:
 
+;; *Note: This package is obsolete.  Use the byte-compiler instead.*
+
 ;; This is a linter for Emacs Lisp.  Currently, it mainly catches
 ;; misspellings and undefined variables, although it can also catch
 ;; function calls with the wrong number of arguments.
@@ -243,7 +246,11 @@ This environment can be passed to `macroexpand'."
 ;;;###autoload
 (defun elint-file (file)
   "Lint the file FILE."
+  (declare (obsolete nil "31.1"))
   (interactive "fElint file: ")
+  (elint--file file))
+
+(defun elint--file (file)
   (setq file (expand-file-name file))
   (or elint-builtin-variables
       (elint-initialize))
@@ -277,6 +284,7 @@ This environment can be passed to `macroexpand'."
 (defun elint-directory (directory)
   "Lint all the .el files in DIRECTORY.
 A complicated directory may require a lot of memory."
+  (declare (obsolete nil "31.1"))
   (interactive "DElint directory: ")
   (let ((elint-running t))
     (dolist (file (directory-files directory t))
@@ -286,13 +294,14 @@ A complicated directory may require a lot of memory."
 		 (not (auto-save-file-name-p file)))
 	(if (string-match elint-directory-skip-re file)
 	    (message "Skipping file %s" file)
-	  (elint-file file)))))
+	  (elint--file file)))))
   (elint-set-mode-line))
 
 ;;;###autoload
 (defun elint-current-buffer ()
   "Lint the current buffer.
 If necessary, this first calls `elint-initialize'."
+  (declare (obsolete nil "31.1"))
   (interactive)
   (or elint-builtin-variables
       (elint-initialize))
@@ -312,6 +321,7 @@ If necessary, this first calls `elint-initialize'."
 (defun elint-defun ()
   "Lint the function at point.
 If necessary, this first calls `elint-initialize'."
+  (declare (obsolete nil "31.1"))
   (interactive)
   (or elint-builtin-variables
       (elint-initialize))

lisp/progmodes/elisp-mode.el

@@ -106,15 +106,6 @@ All commands in `lisp-mode-shared-map' are inherited by this map."
       :help "Go to the start of the current function definition"]
      ["Up List" up-list
       :help "Go one level up and forward"])
-    ("Linting"
-     ["Lint Defun" elint-defun
-      :help "Lint the function at point"]
-     ["Lint Buffer" elint-current-buffer
-      :help "Lint the current buffer"]
-     ["Lint File..." elint-file
-      :help "Lint a file"]
-     ["Lint Directory..." elint-directory
-      :help "Lint a directory"])
     ("Profiling"
      ;; Maybe this should be in a separate submenu from the ELP stuff?
      ["Start Native Profiler..." profiler-start