Add ..versionadded for sys.int_info, update py3k version of
whatsnew/2.7.rst to keep it in sync with the trunk version, and
replace SHIFT with PyLong_SHIFT in #error message
diff --git a/Doc/whatsnew/2.7.rst b/Doc/whatsnew/2.7.rst
index 8037b13..e44a42b 100644
--- a/Doc/whatsnew/2.7.rst
+++ b/Doc/whatsnew/2.7.rst
@@ -86,6 +86,30 @@
(Contributed by Fredrik Johansson and Victor Stinner; :issue:`3439`.)
+* Integers are now stored internally either in base 2**15 or in base
+ 2**30, the base being determined at build time. Previously, they
+ were always stored in base 2**15. Using base 2**30 gives
+ significant performance improvements on 64-bit machines, but
+ benchmark results on 32-bit machines have been mixed. Therefore,
+ the default is to use base 2**30 on 64-bit machines and base 2**15
+ on 32-bit machines; on Unix, there's a new configure option
+ --enable-big-digits that can be used to override this default.
+
+ Apart from the performance improvements this change should be
+ invisible to end users, with one exception: for testing and
+ debugging purposes there's a new structseq ``sys.long_info`` that
+ provides information about the internal format, giving the number of
+ bits per digit and the size in bytes of the C type used to store
+ each digit::
+
+ >>> import sys
+ >>> sys.long_info
+ sys.long_info(bits_per_digit=30, sizeof_digit=4)
+
+
+ (Contributed by Mark Dickinson; :issue:`4258`.)
+
+
.. ======================================================================