celluloid/celluloid — pull request #298 by halorgium (2013-07-16 23:52:57+00:00)
Title: InternalPool does not support non-Celluloid threads being created

If a new `Thread` is created within a `Celluloid::Thread`, that thread is in the pool's `ThreadGroup`.

This means that we are now tracking a `Thread` which is not created by us.

@aflatter discovered [this](https://gist.github.com/aflatter/ff20c9763b768b623956).