RE: Pretest begins end-June

[Drew Adams]

> > (let ((pop-up-frames t)) (pop-to-buffer buffer))
> 
> The part I don't understand is why we can't preserve backward
> compatibility for such code.

It is not just, or even most importantly, about backward compatibility.  Being
able to determine/regulate the behavior with a dynamic binding is an important
feature.  This change would apparently remove/limit that possibility.