bug#57434: 28.1.91; Terminal Emacs Mac OS flickering.

[Eli Zaretskii]

> From: Dmitrii Kuragin <kuragin@google.com>
> Date: Mon, 29 Aug 2022 12:26:07 -0700
> Cc: Gerd Möllmann <gerd.moellmann@gmail.com>, 
>       57434@debbugs.gnu.org
> 
> I tried different terminal emulators, Alacritty, iTerm2, Terminal.app 
> (stock). All of them show the same issue.
> So, it is not a terminal emulator.

If this happens with all terminal emulators on macOS, we should reset
the line_ins_del_ok flag for macOS.  Look in term.c, where it is
initialized by consulting various terminfo features supported by the
terminal.  If all the features it consults indeed work on macOS, then
simply say something like

  #ifdef DARWIN_OS
    tty->line_ins_del_ok = 0;
  #else
  ... the current code...
  #endif

and see if the problem goes away.

Gerd, do you see the same on your system?