stack overflow is basically broken

[Marc Espie]

The routines to detect stack overflow throuh segv  are basically
broken. The idea may be fine, but it ends up calling a sigv handler
that uses gettext, printf, stdout... all of which are definitely NOT
sig-safe.  Pity, because the hardcode routine is basically very careful
to use write(2), to avoid this.

I haven't checked that translation magic is signal-safe.
- I doubt it;
- stdio is not signal-safe in any kind of portable setting anyways.