Issue #27473: Fixed possible integer overflow in bytes and bytearray

concatenations.  Patch by Xiang Zhang.

diff --cc Misc/NEWS
index 6c646b6f486550b0ac4533453f5170591023165f,7d89264f30e038cbbe1b26285dafeb14dee37535..de83c786749ad40d412e285d3cf19b77ddd27e31
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -10,11 -10,9 +10,14 @@@ What's New in Python 3.6.0 alpha 
  Core and Builtins
  -----------------
  
+ - Issue #27473: Fixed possible integer overflow in bytes and bytearray
+   concatenations.  Patch by Xiang Zhang.
+ 
 +- Issue #23034: The output of a special Python build with defined COUNT_ALLOCS,
 +  SHOW_ALLOC_COUNT or SHOW_TRACK_COUNT macros is now off by  default.  It can
 +  be re-enabled using the "-X showalloccount" option.  It now outputs to stderr
 +  instead of stdout.
 +
  - Issue #27443: __length_hint__() of bytearray itearator no longer return
    negative integer for resized bytearray.
  

diff --cc Objects/bytearrayobject.c
Simple merge

diff --cc Objects/bytesobject.c
Simple merge