FYI, trunk bootstrap segfaults with nonzero MALLOC_PERTURB_

[Jim Meyering]

Just to let you know that I'm once again seeing temacs segfault
when MALLOC_PERTURB_ is nonzero.  I was able to bootstrap by with
MALLOC_PERTURB_=0, but with it set to a nonzero value, temacs gets the
(sporadically usual, over the years, now) segfault.

This is on Fedora 17/x86_64 using gcc version 4.8.0 20120604.

When I use F17's current default gcc (version 4.7.0 20120507),
(still with nonzero MALLOC_PERTURB_) I get a slightly different failure:

    make[3]: *** [dired-aux.elc] Segmentation fault (core dumped)