If you created a weakref in an object's __del__ method to itself it would
segfault the interpreter during weakref clean up.  Now any new weakrefs created
after __del__ is run are removed silently.

Fixes bug #1377858 and the weakref_in_del crasher for new-style classes.
Classic classes are still affected.
diff --git a/Misc/NEWS b/Misc/NEWS
index fc5dd66..fccc50d 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,9 @@
 Core and builtins
 -----------------
 
+- Bug #1377858: Fix the segfaulting of the interpreter when an object created
+  a weakref on itself during a __del__ call.
+
 - Bug #1579370: Make PyTraceBack_Here use the current thread, not the
   frame's thread state.