bug#53991: Fix header mangling by message-hide-headers

[Philip Kaludercic]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> Philip Kaludercic <philipk@posteo.net> writes:
>
>> The more complex solution is attached below, and involves replacing the
>> manual end-of-headers tracking with a marker, that resolves the issue
>> that the previous implementation had, where end-of-headers could point
>> right into the middle of a header as described above.
>
> Looks good to me; pushed to Emacs 29.

As this issue presumably also affects older versions (the code hasn't
changed for years), should it also be applied to emacs-28?

-- 
        Philip Kaludercic