bug#57727: 29.0.50; Optimize tty display updates

[Gerd Möllmann]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> Perhaps adding a defcustom for this where the :set calls
> `tty--set-output-buffer-size' might be a nice interface?

ATM, this is terminal-specific, so we'd need some way of specifying for
which frames, terminals or what this option applies.

(I'm assuming from the code that Emacs allows opening frames on multiple
ttys, which was news to me, but that doesn't mean anything of course.)