bug#11934: 24.1; provide variable for pp.el to control max display width

[Drew Adams]

> > > Another challenge is what to do if we have already
> > > nearly exhausted the width limit.
> >
> > Not sure what you mean, there.
> 
> I mean what we do with code that is very nested so that the indentation
> becomes a large amount of the maximum specified width (or even larger).
> 
> Then we should not end up with something like e.g.
> 
> (a (b (c .... (1;limit is here at the colon
>                2
>                3
>                4
>                5
>               )
>            )))

Ah, right.  I think we should try for something at
least a little bit better, for now.  There will no doubt
be room for improvement after that.  And things can no
doubt get complicated, with various tradeoffs possible.

One way to handle tradeoffs, perhaps, is to allow optional
arguments that let callers indicate which behaviors to
choose, among several whose effects might conflict.