GUnixOutputStream can block on close()
While reading through code, I noticed that g_unix_output_stream_close_async()
just calls the blocking close implmentation.
It used to not do that, but in the GTask port this got removed without comment - see 669505e3 - the commit message or associated bug at https://bugzilla.gnome.org/show_bug.cgi?id=661767 don't seem to mention that this is intended, so I'm opening this issue.