bug#63811: 29.0.91; todo-mode item editing bugs

[Eli Zaretskii]

> From: Stephen Berman <stephen.berman@gmx.net>
> Date: Wed, 31 May 2023 11:12:32 +0200
> 
> I have encountered several bugs in todo-mode when creating and editing
> todo items.  I have fixes for them and since I'm the todo-mode
> maintainer I intend to push them to the Savannah repo when I get a bug
> number and clearance for which branch to push to.  The bugs are
> long-standing, at least since Emacs 28 and probably earlier.  The fixes
> touch no code outside of todo-mode.el and seem low-risk; in my testing
> they work as expected.  I've attached a diff against emacs-29 below (the
> todo-mode.el files in current emacs-29 and master are identical).

Assuming all the tests still pass after these changes, please go ahead
and install on emacs-29, and thanks.