Trying to use port audio and threads, and noticed when --threads:on is set, the callbacks don't get called.
Simplest repro is the portaudio library [example](https://bitbucket.org/BitPuffin/nim-portaudio/src/1ee68c6cb001/examples/saw_out.nim?at=default&fileviewer=file-view-default) c -r saw_out.nim works for me c -r --threads:on saw_out.nim no sound, callback is not getting called at all, and the StopStream hangs indefinitely. This is on OSX. I would love to understand what's going on here
