They're actually used as a hackish intrusive list around GQueue so using
a different allocator is rather dangerous. Or rather, this is generally
dangerous and shouldn't be done but ...
Also make sure to free items manually in finalize() so that any
contained buffers can also be unreffed.
We don't want to run it every time a strong reference is dropped but
only at the very end. Otherwise dropping the socket stream will cause a
panic because the socket itself is still running.
This can only happen if the receiver is dropped, which only happens when
the task is stopped. As such, Flushing should be returned instead of
panicking.
