Various asyncio internals expect that the default executor is a
`ThreadPoolExecutor`, so deprecate passing anything else to
`loop.set_default_executor()`.

Initial patch by R. David Murray.

Serhiy Storchaka pointed out that using test.support.unlink was preferable

Co-authored-by: Petr Viktorin <encukou@gmail.com>

Clarify how to bind to all interfaces using socket

<!-- issue-number: bpo-5978 -->
https://bugs.python.org/issue5978
<!-- /issue-number -->

Mathematically, bitwise operations on integers behave as if there were an
infinite number of sign bits. Pragmatically, that gives the same answer as
using one extra sign bit for the bitwise logical operations.

Unused since commit ab994ed8.

/usr/local/lib/pythonX.Y is used by Homebrew's Python already.

Also, update the list of exceptions that may raised by PyMarshal_*
functions. We usually don't document exceptions raised by a
function, but in this case most of them were already documented
in C API and standard library documentation.

* bpo-34239: Convert test_bz2 to use tempfile

test_bz2 currently uses the test.support.TESTFN functionality which creates a temporary file local to the test directory named around the pid.

This can give rise to race conditions where tests are competing with each other to delete and recreate the file.

This change converts the tests to use tempfile.mkstemp which gives a different file every time from the system's temp area

Remove extra `(s)` in the documentation of `compound_stmts`.

* Config: Rename ignore_environment field to use_environment.
* _PyCoreConfig_Read(): if isolated is set, use_environment and
  site_import are now always set to 0.
* Inline pymain_free_raw() into pymain_free()
* Move config_init_warnoptions() call into pymain_read_conf_impl()
* _PyCoreConfig_Read(): don't replace values if they are already set:
  faulthandler, pycache_prefix, home.

Attributes skipinitialspace, doublequote and strict are now
booleans instead of integers 0 or 1.

* Inline cmdline_get_env_flags() into config_read_env_vars():
  _PyCoreConfig_Read() now reads much more environment variables like
  PYTHONVERBOSE.
* Allow to override faulthandler and allocator even if dev_mode=1.
  PYTHONMALLOC is now the priority over PYTHONDEVMODE.
* Fix _PyCoreConfig_Copy(): copy also install_signal_handlers,
  coerce_c_locale and coerce_c_locale_warn
* _PyCoreConfig.install_signal_handlers default is now 1: install
  signals by default
* Fix also a compiler warning: don't define _PyPathConfig type twice.

Enable and fix SMTPUTF8SimTests in test_smtplib.

The tests for SMTPUTF8SimTests in test_smtplib.py were not actually
being run because test_smtplib was still using the 'test_main' pattern,
and the class was never added to test_main.

Additionally, one of the tests needed to be moved to the non-UTF8 server
class because it relies on the server not being UTF-8 compatible (and it
had a bug in in).

PYTHONTRACEMALLOC=0 environment variable and -X tracemalloc=0 command
line option are now allowed to disable explicitly tracemalloc at
startup.

On Windows, passing a negative value to local results in an OSError because localtime_s on Windows does not support negative timestamps. Unfortunately this means that fold detection for timestamps between 0 and max_fold_seconds will result in this OSError since we subtract max_fold_seconds from the timestamp to detect a fold. However, since we know there haven't been any folds in the interval [0, max_fold_seconds) in any timezone, we can hackily just forego fold detection for this time range on Windows.

* Fix case-sensitive comparison

test_nt_helpers assumed that two versions of a Windows path could be compared case-sensitively. This is not the case, and the difference can be triggered (apparently) by running the test on a path somewhere below a Junction.