bug#56393: Actually fix the long lines display bug

[Gregory Heytings]

> Would it help if the tick were incremented by the number of inserted (or 
> deleted or replaced) characters (perhaps limited by some reasonable 
> value, like 1000)?  That would be an easy change, and I don't think it 
> would break anything, since no current code relies on the exact value of 
> the tick, and the value you get after some non-trivial operation on a 
> buffer is generally unpredictable anyway. Would that make the tick 
> usable for this task?

It would.  In fact it is not even necessary to record the exact number of 
inserted/deleted/replaced characters.

> If you agree, I can make such a change (but feel free to do it 
> yourself).

I just did it, is this what you had in mind?  The tick is incremented 
logarithmically.