bug#36216: 27.0.50; Variable binding depth exceeds max-specpld-size during bootstrap

[Juanma Barranquero]

> That pcase situation is different (not only because pcase is not
> pre-loaded, contrary to cl-generic, but also because this trick is used
> to break a circular dependency, rather than to minimize stack depth).

Still, the trick of skipping the macro-expansion sort of worked with
cl-generic, on normal compilations. Broke bootstrapping. And I accept
it was a bit gross.

> We've been increasing the stack size bit by bit for a long time now
> (and IIRC max-specpld-size is not allocated on the C stack, so we can
> go crazy without any risk of crashing on a small C stack), so:
> No objection from me.

Ok, I'll commit it.

> I do wonder what caused the increase of stack depth, tho: I can't
> remember offhand anything recent that would explain it in this part of
> the code.

The problem does not happen (at least on Windows) on the release branch.

In this case, with max-specpdl-size = 1300 it was working, now it
requires on the order of 1435 or so, which is at least a 10% increment
(likely a bit more, assuming it didn't need exactly 1300 before).
That's not very big, but certainly significant.