Comment 19 for bug 906922

This workaround turns out to cause some regressions in other cases, for example:
http://comments.gmane.org/gmane.comp.emulators.qemu/138180

which seems to be because when we use -R (either explicitly or implicitly because of this patch) we tend to map the guest stack immediately above the guest data/BSS segment. This means brk() will always fail, which is bad news for guest binaries that rely on it.