bpo-32030: Split Py_Main() into subfunctions (#4399)

* 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)
diff --git a/PCbuild/python.vcxproj b/PCbuild/python.vcxproj
index ab9fb05..423e68c 100644
--- a/PCbuild/python.vcxproj
+++ b/PCbuild/python.vcxproj
@@ -57,7 +57,7 @@
   </PropertyGroup>
   <ItemDefinitionGroup>
     <ClCompile>
-      <PreprocessorDefinitions>_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>Py_BUILD_CORE;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
     </ClCompile>
     <Link>
       <SubSystem>Console</SubSystem>
@@ -113,4 +113,4 @@
     </PropertyGroup>
     <WriteLinesToFile File="$(PySourcePath)python.bat" Lines="$(_Content)" Overwrite="true" Condition="'$(_Content)' != '$(_ExistingContent)'" />
   </Target>
-</Project>
\ No newline at end of file
+</Project>