title: in pthread_create(), behavior when args is freed before the created thread exits
body: <p>In <code>pthread_create( *thread, *attr, *start_routine, *arg)</code>, if <code>arg</code> is freed before the created thread exits, what is the behaviour?  I didn't see it described in the specification from Open Group, so it may very well be undefined, I just can't find a place to confirm either way.</p>