Merge from 3.6 (issue #28665).

diff --cc Misc/NEWS
index c463efda6170d3d68a2b0c87a5fbdeaa37995750,24810f05600bc929dfa22a4e647168fec9edab47..9909020aef930ff3603ca1981b662b040a948f03
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -10,6 -10,6 +10,8 @@@ What's New in Python 3.7.0 alpha 
  Core and Builtins
  -----------------
  
++- Issue #28665: Improve speed of the STORE_DEREF opcode by 40%.
++
  - Issue #19398: Extra slash no longer added to sys.path components in case of
    empty compile-time PYTHONPATH components.