Issue #21321: itertools.islice() now releases the reference to the source iterator...

Patch by Anton Afanasyev.

diff --cc Misc/ACKS
Simple merge

diff --cc Misc/NEWS
index 76df8dfff8e1ed26e79e01d6a9f93f1d3731ba9d,7739bcbe0df16b41f69efc7f48153784142a59e7..d39775df18dd7117de678e5c167d1cbe7f52e43a
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -60,17 -39,9 +60,20 @@@ Core and Builtin
  Library
  -------
  
+ - Issue #21321: itertools.islice() now releases the reference to the source
+   iterator when the slice is exhausted.  Patch by Anton Afanasyev.
+ 
 +- Issue #21057: TextIOWrapper now allows the underlying binary stream's
 +  read() or read1() method to return an arbitrary bytes-like object
 +  (such as a memoryview).  Patch by Nikolaus Rath.
 +
 +- Issue #20951: SSLSocket.send() now raises either SSLWantReadError or
 +  SSLWantWriteError on a non-blocking socket if the operation would block.
 +  Previously, it would return 0.  Patch by Nikolaus Rath.
 +
 +- Issue #13248: removed previously deprecated asyncore.dispatcher __getattr__
 +  cheap inheritance hack.
 +
  - Issue #9815: assertRaises now tries to clear references to local variables
    in the exception's traceback.