Call to `c4socket_closed` causes native crash.

A call to c4socket_closed sometimes fails catastrophically. I am seeing this fairly regularly, on Windows and I believe I've seen the same thing on Android.

It seems to happen when the call is made from Java's finalizer thread.

I would research this further before passing it on, but the windows crash seems related to a core update. I have an mdmp file for the Windows failure (which doesn't fit here: I can provide it on request)

Feel free to re-assign back to JAK, if we are making a bad call.