bug#70163: 29.3; hexl-mode incorrect docstring

[Eli Zaretskii <eliz@gnu.org>]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: Thierry Volpiatto <thievol@posteo.net>,  schwab@linux-m68k.org,
>   70163@debbugs.gnu.org
> Date: Thu, 04 Apr 2024 08:54:24 -0400
> 
> > Stefan, why do we inject this ugly blurb into the text we return when
> > the library is not loaded? why not simply return the same as RAW does
> > in those cases?
> 
> Good question.  AFAIK this predates me, so we'd have to ask Richard.
> Maybe \<hexl-mode-map> should simply never expand to anything else than the
> empty string.

Maybe.  But meanwhile, the best I can suggest is this:

diff --git a/lisp/hexl.el b/lisp/hexl.el
index 1288cf4..28441a2 100644
--- a/lisp/hexl.el
+++ b/lisp/hexl.el
@@ -256,10 +256,10 @@ hexl-line-displen
 
 ;;;###autoload
 (defun hexl-mode (&optional arg)
-  "\\<hexl-mode-map>A mode for editing binary files in hex dump format.
-This is not an ordinary major mode; it alters some aspects
+  "A mode for editing binary files in hex dump format.
+\\<hexl-mode-map>This is not an ordinary major mode; it alters some aspects
 of the current mode's behavior, but not all; also, you can exit
-Hexl mode and return to the previous mode using `hexl-mode-exit'.
+Hexl mode and return to the previous mode using \\[hexl-mode-exit].
 
 This function automatically converts a buffer into the hexl format
 using the function `hexlify-buffer'.