SF patch 514641 (Naofumi Honda) - Negative ob_size of LongObjects

Due to the bizarre definition of _PyLong_Copy(), creating an instance
of a subclass of long with a negative value could cause core dumps
later on.  Unfortunately it looks like the behavior of _PyLong_Copy()
is quite intentional, so the fix is more work than feels comfortable.

This fix is almost, but not quite, the code that Naofumi Honda added;
in addition, I added a test case.
diff --git a/Misc/ACKS b/Misc/ACKS
index 28157a4..a3ead13 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -203,6 +203,7 @@
 Albert Hofkamp
 Gerrit Holl
 Philip Homburg
+Naofumi Honda
 Jeffrey Honig
 Rob Hooft
 Brian Hooper