fix issue3120 - don't truncate handles on 64-bit Windows.

This is still messy, realistically PC/_subprocess.c should never cast pointers
to python numbers and back at all.

I don't have a 64-bit windows build environment because microsoft apparently
thinks that should cost money.  Time to watch the buildbots.  It builds and
passes tests on 32-bit windows.
diff --git a/Misc/NEWS b/Misc/NEWS
index dc0dbf3..068a20d 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -141,6 +141,8 @@
   up in the child process to prevent deadlock and report proper thread counts
   if the new process uses the threading module.
 
+- Issue #3120: On 64-bit Windows the subprocess module was truncating handles.
+
 Tests
 -----