Modify subprocess._args_from_interpreter_flags() to handle -X dev
option.

Add also unit tests for test.support.args_from_interpreter_flags()
and test.support.optim_args_from_interpreter_flags().

When Python is build is debug mode (Py_DEBUG), DeprecationWarning,
PendingDeprecationWarning and ImportWarning warnings are now
displayed by default.

test_venv: run "-m pip" and "-m ensurepip._uninstall" with -W
ignore::DeprecationWarning since pip code is not part of Python.

The line number in correct when using the -x option: Py_Main() uses
ungetc() to not skip the first newline character.

The new -X dev command line option now also enables asyncio debug
mode.

Since f299abda
the remove_pyc() method no longer tries to
remove .pyo files.

`BUILD_MAP_UNPACK_WITH_CALL` was duplicated as the opcode for both var-positional and var-keyword arguments. The opcode for the former was updated as `BUILD_TUPLE_UNPACK_WITH_CALL`.

When there is a symlink in the directory path of the standard library.

* Run gzip with separate command line options (Android understands  '-f9' as the name of a file).
* Creation of a hard link is controled by SELinux on Android.

* Drop legacy SSL transport

* Drop unused import

* Fix Windows tests

* Drop never executed on Python 3.4+ code

Remove the following fields from tok_state structure which are now
used unused:

* altwarning: "Issue warning if alternate tabs don't match"
* alterror: "Issue error if alternate tabs don't match"
* alttabsize: "Alternate tab spacing"

Replace alttabsize variable with ALTTABSIZE define.

`kargs` -> `kwargs`

The log_rounds parameter for Blowfish has been replaced with the rounds parameter.

Add a new "developer mode": new "-X dev" command line option to
enable debug checks at runtime.

Changes:

* Add unit tests for -X dev
* test_cmd_line: replace test.support with support.
* Fix _PyRuntimeState_Fini(): Use the same memory allocator
   than _PyRuntimeState_Init().
* Fix _PyMem_GetDefaultRawAllocator()

in regular expressions.

from collections.abc rather than collections.

Parse more env vars in Py_Main():

* Add more options to _PyCoreConfig:

  * faulthandler
  * tracemalloc
  * importtime

* Move code to parse environment variables from _Py_InitializeCore()
  to Py_Main(). This change fixes a regression from Python 3.6:
  PYTHONUNBUFFERED is now read before calling pymain_init_stdio().
* _PyFaulthandler_Init() and _PyTraceMalloc_Init() now take an
  argument to decide if the module has to be enabled at startup.
* tracemalloc_start() is now responsible to check the maximum number
  of frames.

Other changes:

* Cleanup Py_Main():

  * Rename some pymain_xxx() subfunctions
  * Add pymain_run_python() subfunction

* Cleanup Py_NewInterpreter()
* _PyInterpreterState_Enable() now reports failure
* init_hash_secret() now considers pyurandom() failure as an "user
  error": don't fail with abort().
* pymain_optlist_append() and pymain_strdup() now sets err on memory
  allocation failure.

* Don't use "Python runtime" anymore to parse command line options or
  to get environment variables: pymain_init() is now a strict
  separation.
* Use an error message rather than "crashing" directly with
  Py_FatalError(). Limit the number of calls to Py_FatalError(). It
  prepares the code to handle errors more nicely later.
* Warnings options (-W, PYTHONWARNINGS) and "XOptions" (-X) are now
  only added to the sys module once Python core is properly
  initialized.
* _PyMain is now the well identified owner of some important strings
  like: warnings options, XOptions, and the "program name". The
  program name string is now properly freed at exit.
  pymain_free() is now responsible to free the "command" string.
* Rename most methods in Modules/main.c to use a "pymain_" prefix to
  avoid conflits and ease debug.
* Replace _Py_CommandLineDetails_INIT with memset(0)
* Reorder a lot of code to fix the initialization ordering. For
  example, initializing standard streams now comes before parsing
  PYTHONWARNINGS.
* Py_Main() now handles errors when adding warnings options and
  XOptions.
* Add _PyMem_GetDefaultRawAllocator() private function.
* Cleanup _PyMem_Initialize(): remove useless global constants: move
  them into _PyMem_Initialize().
* Call _PyRuntime_Initialize() as soon as possible:
  _PyRuntime_Initialize() now returns an error message on failure.
* Add _PyInitError structure and following macros:

  * _Py_INIT_OK()
  * _Py_INIT_ERR(msg)
  * _Py_INIT_USER_ERR(msg): "user" error, don't abort() in that case
  * _Py_INIT_FAILED(err)

* bpo-32025: Add time.thread_time()

* Add missing #endif

* Add NEWS blurb

* Add docs and whatsnew

* Address review comments

* Review comments

bpo-32011: Revert "Issue #15480: Remove the deprecated and unused TYPE_INT64 code from marshal." (#4381)

Simplify the reverted code.

This reverts commit e9bbe8b8.

* Setting sys.tracebacklimit to 0 or less now suppresses printing tracebacks.
* Setting sys.tracebacklimit to None now causes using the default limit.
* Setting sys.tracebacklimit to an integer larger than LONG_MAX now means using
  the limit LONG_MAX rather than the default limit.
* Fixed integer overflows in the case of more than 2**31 traceback items on
  Windows.
* Fixed output errors handling.

* bpo-32015: Asyncio cycling during simultaneously socket read/write and reconnection

* Tests fix

* Tests fix

* News add

* Add new unit tests