Recent sock.type fix (see bug 32331) makes sock.type checks simpler
in asyncio.

Fix compiler warnings in Py_FinalizeEx(): only define variables if
they are needed, add #ifdef.

Other cleanup changes:

* _PyWarnings_InitWithConfig() is no more needed: call
  _PyWarnings_Init() instead.
* Inline pymain_init_main_interpreter() in its caller. This
  subfunction is no more justifed.

* main.c: add missing #include <fenv.h> on FreeBSD
* indent also other #ifdef in main.c
* cleanup Programs/python.c

The last part of test_close_fds() doesn't match its own comment.
The following assertion always holds because fds_to_keep and open_fds
are disjoint by construction.

self.assertFalse(remaining_fds & fds_to_keep & open_fds,
                 "Some fds not in pass_fds were left open")

Fix the code to match the message in the assertion.

It was introduced in bpo-27169.

Even though Python marks any handles it opens as non-inheritable there
is still a race when using `subprocess.Popen` since creating a process
with redirected stdio requires temporarily creating inheritable handles.
By implementing support for `subprocess.Popen(close_fds=True)` we fix
this race.

In order to implement this we use PROC_THREAD_ATTRIBUTE_HANDLE_LIST
which is available since Windows Vista. Which allows to pass an explicit
list of handles to inherit when creating a process.

This commit also adds `STARTUPINFO.lpAttributeList["handle_list"]`
which can be used to control PROC_THREAD_ATTRIBUTE_HANDLE_LIST
directly.

Constant folding was moved to AST optimizer.
But compiler may emit LOAD_CONSTs + BUILD_TUPLE.
For example, default arguments can be constant tuple
if all arguments are constant.

This commit makes peephole's tuple folding simple.
It doesn't support nested tuples because nested
tuples are folded by AST optimizer already.

bpo-32264

* Use fastpath in asyncio.sleep if delay<0

* Add NEWS entry

Based on tests from #4878

Exactly which locale requests will end up giving
you the "C" locale is actually platform dependent.

A blank locale and "POSIX" will translate to "C"
on most Linux distros, but may not do so on other platforms, so this adjusts the way the tests are structured to better account for that.

This is an initial step towards fixing the current
test failure on Cygwin (hence the issue reference) 

As a result of 92a3c6f4, the compiler complains:

Python/import.c:2311:21: warning: comparison of integers of different signs: 'long' and 'unsigned long' [-Wsign-compare]
    if ((i + n + 1) <= PY_SSIZE_T_MAX / sizeof(struct _inittab)) {
         ~~~~~~~~~  ^  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This overflow is extremely unlikely to happen, but let's avoid undefined
behavior anyway.

bpo-29240, bpo-32030: If the encoding change (C locale coerced or
UTF-8 Mode changed), Py_Main() now reads again the configuration with
the new encoding.

Changes:

* Add _Py_UnixMain() called by main().
* Rename pymain_free_pymain() to pymain_clear_pymain(), it can now be
  called multipled times.
* Rename pymain_parse_cmdline_envvars() to pymain_read_conf().
* Py_Main() now clears orig_argc and orig_argv at exit.
* Remove argv_copy2, Py_Main() doesn't modify argv anymore. There is
  no need anymore to get two copies of the wchar_t** argv.
* _PyCoreConfig: add coerce_c_locale and coerce_c_locale_warn.
* Py_UTF8Mode is now initialized to -1.
* Locale coercion (PEP 538) now respects -I and -E options.

Don't define decode_locale() nor encode_locale() on macOS or Android.

Link to the Format Specification Mini Language section from f-strings' documentation.

Run the child process with -E option to ignore the PYTHONWARNINGS
environment variable.

Add types.ClassMethodDescriptorType for unbound class methods.

It no longer spends much time doing complex calculations and no
longer consumes much memory for creating large constants that will
be dropped later.

This fixes also bpo-21074.

This fixes also bpo-22091.

* Implement functionality
* Add documentation

* Add new fields to _PyMainInterpreterConfig:

  * executable
  * prefix
  * base_prefix
  * exec_prefix
  * base_exec_prefix

* _PySys_EndInit() now sets sys attributes from
  _PyMainInterpreterConfig

Each interpreter now has its core_config and main_config copy:

* Add _PyCoreConfig_Copy() and _PyMainInterpreterConfig_Copy()
* Move _PyCoreConfig_Read(), _PyCoreConfig_Clear() and
  _PyMainInterpreterConfig_Clear() from Python/pylifecycle.c to
  Modules/main.c
* Fix _Py_InitializeEx_Private(): call _PyCoreConfig_ReadEnv() before
  _Py_InitializeCore()

bpo-32329, bpo-32030:

* The -R option now turns on hash randomization when the
  PYTHONHASHSEED environment variable is set to 0 Previously, the
  option was ignored.
* sys.flags.hash_randomization is now properly set to 0 when hash
  randomization is turned off by PYTHONHASHSEED=0.
* _PyCoreConfig_ReadEnv() now reads the PYTHONHASHSEED environment
  variable. _Py_HashRandomization_Init() now only apply the
  configuration, it doesn't read PYTHONHASHSEED anymore.