bpo-39882: Py_FatalError() logs the function name (GH-18819)

The Py_FatalError() function is replaced with a macro which logs
automatically the name of the current function, unless the
Py_LIMITED_API macro is defined.

Changes:

* Add _Py_FatalErrorFunc() function.
* Remove the function name from the message of Py_FatalError() calls
  which included the function name.
* Update tests.
diff --git a/Include/cpython/pyerrors.h b/Include/cpython/pyerrors.h
index f8480fb..ab2e740 100644
--- a/Include/cpython/pyerrors.h
+++ b/Include/cpython/pyerrors.h
@@ -178,6 +178,12 @@
     const char *err_msg,
     PyObject *obj);
 
+PyAPI_FUNC(void) _Py_NO_RETURN _Py_FatalErrorFunc(
+    const char *func,
+    const char *message);
+
+#define Py_FatalError(message) _Py_FatalErrorFunc(__func__, message)
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/Include/pyerrors.h b/Include/pyerrors.h
index 3fd133c..399bb7c 100644
--- a/Include/pyerrors.h
+++ b/Include/pyerrors.h
@@ -21,7 +21,11 @@
 PyAPI_FUNC(void) PyErr_SetExcInfo(PyObject *, PyObject *, PyObject *);
 #endif
 
-/* Defined in Python/pylifecycle.c */
+/* Defined in Python/pylifecycle.c
+
+   The Py_FatalError() function is replaced with a macro which logs
+   automatically the name of the current function, unless the Py_LIMITED_API
+   macro is defined. */
 PyAPI_FUNC(void) _Py_NO_RETURN Py_FatalError(const char *message);
 
 #if defined(Py_DEBUG) || defined(Py_LIMITED_API)