* Add a whole new documentation page:
  "Python Initialization Configuration"
* PyWideStringList_Append() return type is now PyStatus,
  instead of int
* PyInterpreterState_New() now calls PyConfig_Clear() if
  PyConfig_InitPythonConfig() fails.
* Rename files:

  * Python/coreconfig.c => Python/initconfig.c
  * Include/cpython/coreconfig.h => Include/cpython/initconfig.h
  * Include/internal/: pycore_coreconfig.h => pycore_initconfig.h

* Rename structures

  * _PyCoreConfig => PyConfig
  * _PyPreConfig => PyPreConfig
  * _PyInitError => PyStatus
  * _PyWstrList => PyWideStringList

* Rename PyConfig fields:

  * use_module_search_paths => module_search_paths_set
  * module_search_path_env => pythonpath_env

* Rename PyStatus field: _func => func
* PyInterpreterState: rename core_config field to config
* Rename macros and functions:

  * _PyCoreConfig_SetArgv() => PyConfig_SetBytesArgv()
  * _PyCoreConfig_SetWideArgv() => PyConfig_SetArgv()
  * _PyCoreConfig_DecodeLocale() => PyConfig_SetBytesString()
  * _PyInitError_Failed() => PyStatus_Exception()
  * _Py_INIT_ERROR_TYPE_xxx enums => _PyStatus_TYPE_xxx
  * _Py_UnixMain() => Py_BytesMain()
  * _Py_ExitInitError() => Py_ExitStatusException()
  * _Py_PreInitializeFromArgs() => Py_PreInitializeFromBytesArgs()
  * _Py_PreInitializeFromWideArgs() => Py_PreInitializeFromArgs()
  * _Py_PreInitialize() => Py_PreInitialize()
  * _Py_RunMain() => Py_RunMain()
  * _Py_InitializeFromConfig() => Py_InitializeFromConfig()
  * _Py_INIT_XXX() => _PyStatus_XXX()
  * _Py_INIT_FAILED() => _PyStatus_EXCEPTION()

* Rename 'err' PyStatus variables to 'status'
* Convert RUN_CODE() macro to config_run_code() static inline function
* Remove functions:

  * _Py_InitializeFromArgs()
  * _Py_InitializeFromWideArgs()
  * _PyInterpreterState_GetCoreConfig()

The whole coreconfig.h header is now excluded from Py_LIMITED_API.
Move functions definitions into a new internal pycore_coreconfig.h
header.

* Move Include/coreconfig.h to Include/cpython/coreconfig.h
* coreconfig.h header is now excluded from Py_LIMITED_API
* Move functions to pycore_coreconfig.h

Use crypt_r() when available instead of crypt() in the crypt module.

As a nice side effect: This also avoids a memory sanitizer flake as clang msan doesn't know about crypt's internal libc allocated buffer.

Rename our new MEMORY_SANITIZER define to _Py_MEMORY_SANITIZER.
Project based C Preprocessor namespacing at its finest. :P

Adds configure flags for msan and ubsan builds to make it easier to enable.
These also encode the detail that address sanitizer and memory sanitizer
should disable pymalloc.

Define MEMORY_SANITIZER when appropriate at build time and adds workarounds
to existing code to mark things as initialized where the sanitizer is otherwise unable to
determine that.  This lets our build succeed under the memory sanitizer.  not all tests
pass without sanitizer failures yet but we're in pretty good shape after this.

Add pyatomic.h to the VS project (it wasn't referenced).

* Modify object.h to ensure that pymem.h is included,
  to get _Py_tracemalloc_config variable.
* Move _PyTraceMalloc_XXX() functions to tracemalloc.h,
  they need PyObject type. Break circular dependency between pymem.h
  and object.h.

* 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