bug#41357: 28.0.50; GC may miss to mark calle safe register content

[Eli Zaretskii]

> Cc: bug-gnu-emacs@gnu.org
> From: Paul Eggert <eggert@cs.ucla.edu>
> Date: Sun, 17 May 2020 09:46:23 -0700
> 
> The only question in my mind is whether to install the patch into the emacs-27
> branch or the master branch.

Definitely the master!