bpo-43795: PEP-652: Clean up the stable ABI/limited API (GH-25482)

- `_Py_EncodeLocaleRaw`, which is private by name, undocumented,
  and wasn't exported in `python3.dll`, is moved to a private header.
- `_Py_HashSecret_Initialized`, again private by name, undocumented,
  and not exported in `python3.dll`, is excluded with `Py_LIMITED_API`.
- `PyMarshal_*` and `PyMember_*One` functions, declared in private headers and
  not exported in `python3.dll`, are removed from `Doc/data/stable_abi.dat`.
- `PyMem_Calloc` which *was* exported in `python3dll.c`, is moved to public
  headers where it joins its other `PyMem_*` friends.

Only the last change is documented in the blurb; others are not user-visible.
(Nothing uses `Doc/data/stable_abi.dat` yet.)


https://bugs.python.org/issue43795

diff --git a/Include/cpython/fileutils.h b/Include/cpython/fileutils.h
index 312fd95..954f078 100644
--- a/Include/cpython/fileutils.h
+++ b/Include/cpython/fileutils.h
@@ -32,6 +32,9 @@ PyAPI_FUNC(int) _Py_EncodeLocaleEx(
     int current_locale,
     _Py_error_handler errors);
 
+PyAPI_FUNC(char*) _Py_EncodeLocaleRaw(
+    const wchar_t *text,
+    size_t *error_pos);
 
 PyAPI_FUNC(PyObject *) _Py_device_encoding(int);