Run find-function-after-hook after finding a symbol

* lisp/emacs-lisp/find-func.el (find-library):
* lisp/help-mode.el (help-function-def, help-variable-def):
Run `find-function-after-hook' inside the help-function of the
buttons (bug#22583).
* etc/NEWS: Mention the change.

This is a backport from master.
(cherry picked from commit f069d85450)

etc/NEWS

@@ -17,7 +17,10 @@ with a prefix argument or by typing C-u C-h C-n.
 
 
 * Changes in Emacs 25.2
-This is a bug-fix release with no new features.
+This is a bug-fix release with (almost) no new features.
+
+** `find-library', `help-function-def' and `help-variable-def' now run
+`find-function-after-hook'.
 
 
 * Installation Changes in Emacs 25.1

lisp/emacs-lisp/find-func.el

@@ -283,7 +283,11 @@ LIBRARY should be a string (the name of the library)."
 			 "Library name: ")
 		       table nil nil nil nil def))))
   (let ((buf (find-file-noselect (find-library-name library))))
-    (condition-case nil (switch-to-buffer buf) (error (pop-to-buffer buf)))))
+    (condition-case nil
+        (prog1
+            (switch-to-buffer buf)
+          (run-hooks 'find-function-after-hook))
+      (error (pop-to-buffer buf)))))
 
 ;;;###autoload
 (defun find-function-search-for-symbol (symbol type library)

lisp/help-mode.el

@@ -202,6 +202,7 @@ The format is (FUNCTION ARGS...).")
 		   (let ((location
 			  (find-function-search-for-symbol fun type file)))
 		     (pop-to-buffer (car location))
+			 (run-hooks 'find-function-after-hook)
 		     (if (cdr location)
 			 (goto-char (cdr location))
 		       (message "Unable to find location in file"))))
@@ -231,6 +232,7 @@ The format is (FUNCTION ARGS...).")
 		     (setq file (help-C-file-name var 'var)))
 		   (let ((location (find-variable-noselect var file)))
 		     (pop-to-buffer (car location))
+		     (run-hooks 'find-function-after-hook)
 		     (if (cdr location)
 		       (goto-char (cdr location))
 		       (message "Unable to find location in file"))))