Issue #28480: Merge multithreading fixes from 3.6

diff --cc Misc/NEWS
index e525c9bbe352570fd76f249283755964be23c39d,2936e3a329f51e2bbb1a8db525d14c3c8c9a6bed..12ef2ceb61d18627b64188f957f5000748f80ceb
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -88,27 -121,6 +88,30 @@@ Core and Builtin
  Library
  -------
  
++- Issue #28480: Fix error building socket module when multithreading is
++  disabled.
++
 +- Issue #28240: timeit: remove ``-c/--clock`` and ``-t/--time`` command line
 +  options which were deprecated since Python 3.3.
 +
 +- Issue #28240: timeit now repeats the benchmarks 5 times instead of only 3
 +  to make benchmarks more reliable.
 +
 +- Issue #28240: timeit autorange now uses a single loop iteration if the
 +  benchmark takes less than 10 seconds, instead of 10 iterations.
 +  "python3 -m timeit -s 'import time' 'time.sleep(1)'" now takes 4 seconds
 +  instead of 40 seconds.
 +
 +- Distutils.sdist now looks for README and setup.py files with case
 +  sensitivity. This behavior matches that found in Setuptools 6.0 and
 +  later. See `setuptools 100
 +  <https://github.com/pypa/setuptools/issues/100>`_ for rationale.
 +
 +- Issue #24452: Make webbrowser support Chrome on Mac OS X.
 +
 +- Issue #20766: Fix references leaked by pdb in the handling of SIGINT
 +  handlers.
 +
  - Issue #27998: Fixed bytes path support in os.scandir() on Windows.
    Patch by Eryk Sun.
  

diff --cc Modules/socketmodule.c
Simple merge