I've attached my patch that I want to commit.  The main change from
filethread4 is some cleanup in file_test to make it run a lot faster and
add verbose mode output to indicate how well it is actually testing the
problem (counting the times that close raises IOError).

One concern holding up my commit:

Will this test pass on windows?  It is opening and closing the same file
in 'w+' mode from multiple threads of the same process at once.

Can someone with a windows dev environment please apply this patch and
test it.  If it dislikes the above file behavior, can you propose a fix
for it (set windows file non-exclusive flags or whatever you're supposed
to do... the worse alternative would be to use a new filename on each
open but that could cause a nightmare of thousands of new files being
created by the test which then have to be cleaned up)?

thanks,
-gps