Issue #25464: Fixed HList.header_exists() in tkinter.tix module by addin

a workaround to Tix library bug.

diff --cc Lib/tkinter/tix.py
Simple merge

diff --cc Misc/NEWS
index 3f3b995d0a562c59869d20006114b501fe48d6a6,8b99882436be59119db7e6fc95c949140c2a8802..5f005206f7d34a4bd84306257e51daa06af05558
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -16,75 -13,6 +16,78 @@@ Core and Builtin
  - Issue #23782: Fixed possible memory leak in _PyTraceback_Add() and exception
    loss in PyTraceBack_Here().
  
 +- Issue #28471: Fix "Python memory allocator called without holding the GIL"
 +  crash in socket.setblocking.
 +
 +
 +Library
 +-------
 +
++- Issue #25464: Fixed HList.header_exists() in tkinter.tix module by addin
++  a workaround to Tix library bug.
++
 +- Issue #28488: shutil.make_archive() no longer adds entry "./" to ZIP archive.
 +
 +- Issue #25953: re.sub() now raises an error for invalid numerical group
 +  reference in replacement template even if the pattern is not found in
 +  the string.  Error message for invalid group reference now includes the
 +  group index and the position of the reference.
 +  Based on patch by SilentGhost.
 +
 +- Issue #18219: Optimize csv.DictWriter for large number of columns.
 +  Patch by Mariatta Wijaya.
 +
 +- Issue #28448: Fix C implemented asyncio.Future didn't work on Windows.
 +
 +- Issue #28480: Fix error building socket module when multithreading is
 +  disabled.
 +
 +- Issue #24452: Make webbrowser support Chrome on Mac OS X.
 +
 +- Issue #20766: Fix references leaked by pdb in the handling of SIGINT
 +  handlers.
 +
 +- Issue #28492: Fix how StopIteration exception is raised in _asyncio.Future.
 +
 +- Issue #28500: Fix asyncio to handle async gens GC from another thread.
 +
 +- Issue #26923: Fix asyncio.Gather to refuse being cancelled once all
 +  children are done.
 +  Patch by Johannes Ebke.
 +
 +- Issue #26796: Don't configure the number of workers for default
 +  threadpool executor.
 +  Initial patch by Hans Lawrenz.
 +
 +Build
 +-----
 +
 +- Issue #28208: Update Windows build to use SQLite 3.14.2.0.
 +
 +- Issue #28248: Update Windows build to use OpenSSL 1.0.2j.
 +
 +Tests
 +-----
 +
 +- Issue #26944: Fix test_posix for Android where 'id -G' is entirely wrong or
 +  missing the effective gid.
 +
 +- Issue #28409: regrtest: fix the parser of command line arguments.
 +
 +
 +What's New in Python 3.6.0 beta 2
 +=================================
 +
 +*Release date: 2016-10-10*
 +
 +Core and Builtins
 +-----------------
 +
 +- Issue #28183: Optimize and cleanup dict iteration.
 +
 +- Issue #26081: Added C implementation of asyncio.Future.
 +  Original patch by Yury Selivanov.
 +
  - Issue #28379: Added sanity checks and tests for PyUnicode_CopyCharacters().
    Patch by Xiang Zhang.