As per previous discussion, it was decided that the Stream classes
should be constructed on the heap.
While I don't personally agree with this change, it does have the
benefit of avoiding Function object reconstructions due to the lambda
passed to Notifier pointing to a stale object reference. This also has
the benefit of not having to "box" objects for virtual usage, as the
objects come pre-boxed.
However, it means that we now hit the heap everytime we construct a
TCPSocket for instance, which might not be desirable.
It was possible for the "local_socket_read" and "local_socket_write"
tests to fail because we had exited the EventLoop before
BackgroundAction got around to invoking the completion callback.
The crash happened when trying to deferred_invoke() on the background
thread, calling Core::EventLoop::current() after said EventLoop had
returned from exec().
Fix this by not passing a completion callback, since we didn't need
one in the first place.
