[plt-scheme] Compile MzScheme to use OS threads

Pinku Surana wrote:
> In "Inside PLT MzScheme", it says MzScheme is basically a single
> threaded runtime. But way back in version 103p, it says: "On a few
> platforms, including Windows, Solaris, and Linux, MzScheme can be
> compiled to map each Scheme thread to a separate operating system
> thread. The advantage of the OS-thread configuration is that different
> Scheme threads can take advantage of different processors on a multi-
> processor machine."
>  
> That's what I want. Has support for this been removed, or is it still 
> possible to compile
> mzscheme to use OS threads? How? I compiled with pthreads, but that
> didn't appear to work.
>

Removed.

Chongkai