bug#21072: Brave new mark-defun (and a testing tool)

[Stefan Monnier]

>>> 1. What is the difference between (debug t) and (debug form body)?  From
>>> my understanding of the manual, there seems to be none.
>> Indeed, no significant difference.
> Oops, I meant (debug sexp body), then I changed it for some reason and
> forgot to change back to the correct thing.

Ah that changes everything: (debug (sexp body)) is quite different from
(debug t) since it says that the first argument is not an expression
(and hence shouldn't be instrumented).


        Stefan