gsoc_threads branch feedback

[Nat Tuck]

Hey All,

Now that Google Summer of Code is over, I've got this gsoc_threads
branch that could use some testing and comments. The bad news is that
it doesn't actually let you run threads in parallel on multiple CPUs.
The good news is that it does let you write code in a concurrent style
and do blocking file input without blocking other concurrent tasks.

Even if you don't have the couple hours to pull down the branch and
take a look, you might be able to help me with a couple other
questions:

- Does the Task API I've implemented[1] make sense?
- Is there anything important missing?
- What blocking operations should I be handling aside from file input?

Here are some links to blog posts with more information:
[1] https://www.parrot.org/content/green-threads-task-api
[2] https://www.parrot.org/content/hybrid-threads-gsoc-project-results
[3] https://www.parrot.org/content/green-threads-classic-example

Thanks,

-- Nat Tuck, aka Chandon