Prevent expandtabs() on string and unicode objects from causing a segfault when
a large width is passed on 32-bit platforms.  Found by Google.

It would be good for people to review this especially carefully and verify
I don't have an off by one error and there is no other way to cause overflow.
diff --git a/Misc/NEWS b/Misc/NEWS
index 73149fb..ad5fd5c 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,9 @@
 Core and builtins
 -----------------
 
+- Prevent expandtabs() on string and unicode objects from causing a segfault when
+  a large width is passed on 32-bit platforms.
+
 - Bug #1733488: Fix compilation of bufferobject.c on AIX.
 
 - Bug #1722485: remove docstrings again when running with -OO.