Added missing .grab_release() calls to all places where we call .grab_set().

bpo-31650, bpo-34170: Replace _Py_CheckHashBasedPycsMode with
_PyCoreConfig._check_hash_pycs_mode. Modify PyInit__imp() and
zipimport to get the parameter from the current interpreter core
configuration.

Remove Include/internal/import.h file.

* Add Include/coreconfig.h
* Move config_*() and _PyCoreConfig_*() functions from Modules/main.c
  to a new Python/coreconfig.c file.
* Inline _Py_ReadHashSeed() into config_init_hash_seed()
* Move global configuration variables to coreconfig.c

Fix a memory leak in pymain_init_pycache_prefix()
when PYTHONPYCACHEPREFIX and -X pycache_prefix are used.

Add unit tests for argc and argv of _PyCoreConfig.

* Rename _PyCoreConfig.unbuffered_stdio to buffered_stdio
* Rename _PyCoreConfig.debug to parser_debug

Modify frozenmain.c to use _Py_InitializeFromConfig().

Fix a crash on negative STACKADJ() when Low-Level trace (LLTRACE) is enabled.

* Fix integer overflow in os.readv(), os.writev(), os.preadv()
  and os.pwritev() and in os.sendfile() with headers or trailers
  arguments (on BSD-based OSes and MacOS).

* Fix sending the part of the file in os.sendfile() on MacOS.
  Using the trailers argument could cause sending more bytes from
  the input file than was specified.

Thanks Ned Deily for testing on 32-bit MacOS.

* help(hashlib) didn't work because of incorrect module name in blake2b and
  blake2s classes.
* Constructors blake2*(), sha3_*(), shake_*() and keccak_*() incorrectly
  accepted keyword argument "string" for binary data, but documented as
  accepting the "data" keyword argument. Now this parameter is positional-only.
* Keyword-only parameters in blake2b() and blake2s() were not documented as
  keyword-only.
* Default value for some parameters of blake2b() and blake2s() was None,
  which is not acceptable value.
* The length argument for shake_*.digest() was wrapped out to 32 bits.
* The argument for shake_128.digest() and shake_128.hexdigest() was not
  positional-only as intended.
* TypeError messages for incorrect arguments in all constructors sha3_*(),
  shake_*() and keccak_*() incorrectly referred to sha3_224.

Also made the following enhancements:

* More accurately specified input and result types for strings, bytes and
  bytes-like objects.
* Unified positional parameter names for update() and constructors.
* Improved formatting.

 Revert "closes bpo-27494: Fix 2to3 handling of trailing comma after a generator expression (GH-3771)" (#8241)

This reverts commit af810b35.

This is not valid syntax (see bpo-32012).

* The hash of BuiltinMethodType instances no longer depends on the hash
  of __self__. It depends now on the hash of id(__self__).
* The hash and equality of ModuleType and MethodWrapperType instances no
  longer depend on the hash and equality of __self__. They depend now on
  the hash and equality of id(__self__).
* MethodWrapperType instances no longer support ordering.

This list is never used: if detect_types is on, this list will be
replaced with another one before row_cast_map is used, if
detect_types is off, row_cast_map is not used at all.

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.