bug#56393: Turn on narrowing in redisplay_window

[Gerd Möllmann]

Gregory Heytings <gregory@heytings.org> writes:

>>
>> which is "the buffer got smaller"?
>>
>
> You are correct.  It's too hot here too, apparently!  😉

Is finding newlines that expensive?  (I don't remember.)  I mean, if
someone turns that "mode" on, does he deserve to suffer a little bit
while that is switched on?

I think someone with such a long line deserves to suffer.