python threads on multi-CPU machines

[Kevin Cazabon]

> However, C extensions can release the
> GIL, and almost all I/O code in Python does that, so I/O-heavy programs
> will make good use of the SMP.

FYI, I'm also working on adding that functionality to the PIL library,
seeing as imaging operations can be fairly expensive too.  It makes
these processes more "friendly" to other threads (and Tk) even on
single-CPU boxes, and allows taking advantage of multiple CPUs where
available.

I'll be posting links on the PIL mailing list when it's complete (just
needs exhaustive testing now... it'll be a while), and Fred has agreed
to merge it into the core distribution afterwards.

Kevin.