[Patches] GNU pth thread library support

[Guido van Rossum]

> This patch adds the ability for Python to use the GNU pth threading
> library. pth is a non-preemptive user-space threading library. For more
> information, see http://www.gnu.org/software/pth. It presently has only
> been tested on Linux. And of course it's against current CVS...
> 
> Buglets: Some annoying compiler warnings about socketbits.h. The
> configuration could probably be better: It may conflict if other threading
> libraries (other than pthreads) are installed.

Andy,

I've applied your patch -- I don't know anything about GNU pth, but it
seems your patch doesn't affect anything when GNU pth is not
installed, so I'm fine with it.

One thing: you sent in a change to config.h.in.  That's not how it's
done -- you add symbols to acconfig.h (in the proper alphabetical
order!), and they automatically get added to config.h.in when you run
autoheader.  I fixed this by adding _GNU_PTH to acconfig.h; I didn't
see any references to the HAVE_PTH_INIT symbol in your code so I left
that out.

Realize that I don't have the time to maintain or debug this -- if a
conflict is reported with the configuration during the alpha cycle,
it's up to you to fix it.

--Guido van Rossum (home page: http://www.python.org/~guido/)