Patch contributed by Bohuslav "Slavek" Kabrda (bkabrda)

This means we can remove our usage of qsort() than relied on undefined behavior.

Backport by Zbigniew Halas.

in itertools module (i.e. itertools.izip(), itertools.chain(), etc).

This was already done in Python3, but having it wrong leads to
incorrect debug output, so it seems worth fixing in 2.7 as well.

Patch by Victor Terrón.