local refs

[Matthew Fluet]

> > I agree that the fix is local, but it "alters" the HandlerPush/Pop
> > structure of the program in a non-trivial(?) way.
> 
> I disagree.  It's a push right before the nontail call and a pop right
> after the return or handle.

(devil's advocate:) if it is o.k. to turn any handler at a non-tail call
into a "push right before a nontail call and popp right after the return
or handle", then why bother maintaining HandlerPush/Pop at all.

I'm not commenting on the complication of the transformation, I'm talking
about how significantly the program deviates from the original.