(GNU/Hurd is not dead)

So failed to load tcl/tk dll because $(dist)/tcltk/bin was set to PATH as
relative path. (Windows)

Previous commit changed macpath but macpath is not used anymore as os.path

directly. It used to be built with bzip2's makefile.

Store all errors signaling a disconnection into a global frozenset to save some computation time on recv() and send().

independent of the locale. Set LC_ALL=C too.

module.

Closes issue #9848. Thanks to Arfrever Frehtes Taifersar Arahesis for the bug
report.

The forward links are hard references.
The sentinel element is also a weakref proxy
(to break a forward cylce wrapping around the sentinel).

handles non-blocking readinto() returning None correctly.