malloc(0) returning 0 is expected behavior on AIX but
compiling with -D_LINUX_SOURCE_COMPAT, malloc(0) should
return a valid pointer (which we do define for AIX). However,
including cstdlib resets the behaviour of _LINUX_SOURCE_COMPAT.
GCC bug: 79839

R=jochen@chromium.org, titzer@chromium.org
BUG=
LOG=N

Review-Url: https://codereview.chromium.org/2732743002
Cr-Commit-Position: refs/heads/master@{#43647}