_PyUnicode_FromId() may return NULL.

Reported by coverity scan: CID 1426868, 1426867.

This is more complicated than it should be because we need to preserve the
useful mtime-based regeneration feature that lib2to3.pgen2.driver.load_grammar
has. We only look for the pickled grammar file with pkgutil.get_data and only if
the source file does not exist.

Skip the test which fails on FreeBSD with POSIX locale.

Skip the test to fix FreeBSD buildbots, until a fix can be found, so
the buildbots can catch other regressions.

Skip the test failing randomly because of known race condition.

Skip the test to fix macOS buildbots until a decision is made on the
proper fix for the race condition.

Add a new _Py_FindEnvConfigValue() function: code shared between
Windows and Unix implementations of _PyPathConfig_Calculate() to read
the pyenv.cfg file.

_Py_FindEnvConfigValue() now uses _Py_DecodeUTF8_surrogateescape()
instead of using a Python Unicode string, the Python API must not be
used early during Python initialization. Same change in Unix
search_for_exec_prefix(): use _Py_DecodeUTF8_surrogateescape().

Cleanup also encode_current_locale(): PyMem_RawFree/PyMem_Free can be
called with NULL.

Fix also "NUL byte" => "NULL byte" typo.

Replace Py_EncodeLocale() with _Py_EncodeLocaleRaw() in:

* _Py_wfopen()
* _Py_wreadlink()
* _Py_wrealpath()
* _Py_wstat()
* pymain_open_filename()

These functions are called early during Python intialization, only
the RAW memory allocator must be used.

Py_EncodeLocale() now uses _Py_EncodeUTF8_surrogateescape(), instead
of using temporary unicode and bytes objects. So Py_EncodeLocale()
doesn't use the Python C API anymore.

Closes bpo-15873.

* _Py_InitializeCore() doesn't call _PyMem_SetupAllocators() anymore
  if the PYTHONMALLOC environment variable is not set.
* pymain_cmdline() now sets the allocator to the default, instead of
  setting the allocator in subfunctions.
* Py_SetStandardStreamEncoding() now calls
  _PyMem_SetDefaultAllocator() to get a known allocator, to be able
  to release the memory with the same allocator.

* Add _PyCoreConfig.install_signal_handlers
* Remove _PyMain.config: _PyMainInterpreterConfig usage is now
  restricted to pymain_init_python_main().
* Rename _PyMain.core_config to _PyMain.config
* _PyMainInterpreterConfig_Read() now creates the xoptions dictionary
   from the core config
* Fix _PyMainInterpreterConfig_Read(): don't replace xoptions and
  argv if they are already set.

* Make ssh_handshake_timeout None by default.
* Raise ValueError if ssl_handshake_timeout is used without ssl.
* Raise ValueError if ssl_handshake_timeout is not positive.

The built-in map() function collects function arguments lazily, but concurrent.futures.Executor.map() does so eagerly.

Use tuples and raw arrays instead of lists.

Merge _PyCoreConfig_ReadEnv() into _PyCoreConfig_Read(), and
_Py_CommandLineDetails usage is now restricted to pymain_cmdline().

Changes:

* _PyCoreConfig: Add nxoption, xoptions, nwarnoption and warnoptions
* Add _PyCoreConfig.program: argv[0] or ""
* Move filename, command, module and xoptions from
  _Py_CommandLineDetails to _PyMain. xoptions _Py_OptList becomes
  (int, wchar_t**) list.
* Add pymain_cmdline() function
* Rename copy_argv() to copy_wstrlist(). Rename clear_argv() to
  clear_wstrlist(). Remove _Py_OptList structure: use (int,
  wchar_t**) list instead.
* Rename pymain_set_flag_from_env() to pymain_get_env_flag()
* Rename pymain_set_flags_from_env() to pymain_get_env_flags()
* _PyMainInterpreterConfig_Read() now creates the warnoptions from
  _PyCoreConfig.warnoptions
* Inline pymain_add_warning_dev_mode() and
  pymain_add_warning_bytes_flag() into config_init_warnoptions()
* Inline pymain_get_program_name() into _PyCoreConfig_Read()
* _Py_CommandLineDetails: Replace warning_options with nwarnoption
  and warnoptions. Replace env_warning_options with nenv_warnoption
  and env_warnoptions.
* pymain_warnings_envvar() now has a single implementation for
  Windows and Unix: use config_get_env_var_dup() to also get the
  variable as wchar_t* on Unix.

* bpo-32379: Faster MRO computation for single inheritance

Change atexit behavior and PEP-489 multiphase init support.

* Reorganize pymain_main() to make the code more flat
* Clear configurations before pymain_update_sys_path()
* Mark Py_FatalError() and _Py_FatalInitError() with _Py_NO_RETURN
* Replace _PyMain.run_code variable with a new RUN_CODE() macro
* Move _PyMain.cf into a local variable in pymain_run_python()

* Add argc and argv to _PyCoreConfig
* _PyMainInterpreterConfig_Read() now builds its argv from
  _PyCoreConfig.arg
* Move _PyMain.env_warning_options into _Py_CommandLineDetails
* Reorder pymain_free()

Mention that the format-specifier mini language in f-strings
is the same one used by str.format.

10 seconds by default.

* Fix #32377: improve __del__ docs and fix mention about resurrection

* Mention that CPython only calls __del__ once.

Implement find_library() support in ctypes/util for AIX.

Add some AIX specific tests.