[Patches] Change to reference-dump procedure at shutdown

[Guido van Rossum]

> This patch only affects debug builds with Py_TRACE_REFS defined.  This is the default for debug builds on Windows.
> 
> At shutdown, Python offers to dump the remaining references.  This upsets a few programs, such as debug COM servers, or any program that uses 'sys.executable' to launch a child-process.  The process never terminates, as it is waiting to find out if you want the references dumped.
> 
> Further, simply starting and closing the Python interpreter on Windows results in over 2000 references - its unlikely people want to print them that often :-)
> 
> The patch below only offers to dump the references if the environment variable PYTHONDUMPREFS is set.  Otherwise, it still prints the number of references, but immediately terminates.
> 
> If this patch is acceptable and it is felt this variable should be documented, let me know, and I will try and hunt down all the relevant places - but IMO, anyone who really needs these references dumped is likely to see this code :-)

Mark, shouldn't this be enclosed in an #ifdef MS_WINDOWS bracket?

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