bpo-36142: Move command line parsing to coreconfig.c (GH-12123)

* Add _PyCoreConfig_ReadFromArgv() function which parses command line
  options: move code from main.c to coreconfig.c.
* Add _PyCoreConfig_Write() to write the new configuration: coerce
  the LC_CTYPE locale, set Py_xxx global configuration variables,
  etc.
* _PyCoreConfig_ReadFromArgv() now only changes the LC_CTYPE locale
  temporarily. _PyCoreConfig_Write() becomes responsible to set the
  LC_CTYPE locale.
* Add _Py_SetArgcArgv() and _Py_ClearArgcArgv() functions
* Rename many "pymain_xxx()" functions
* Add "const" to some function parameters
* Reorganize main.c to declare functions in the order in which they
  are called.

Include/cpython/coreconfig.h

@@ -5,6 +5,16 @@
 extern "C" {
 #endif
 
+/* _PyArgv */
+
+typedef struct {
+    int argc;
+    int use_bytes_argv;
+    char **bytes_argv;
+    wchar_t **wchar_argv;
+} _PyArgv;
+
+
 /* _PyInitError */
 
 typedef struct {

Include/internal/pycore_coreconfig.h

@@ -8,6 +8,29 @@ extern "C" {
 #  error "this header requires Py_BUILD_CORE or Py_BUILD_CORE_BUILTIN defined"
 #endif
 
+/* _Py_wstrlist */
+
+PyAPI_FUNC(void) _Py_wstrlist_clear(
+    int len,
+    wchar_t **list);
+PyAPI_FUNC(wchar_t**) _Py_wstrlist_copy(
+    int len,
+    wchar_t * const *list);
+PyAPI_FUNC(_PyInitError) _Py_wstrlist_append(
+    int *len,
+    wchar_t ***list,
+    const wchar_t *str);
+PyAPI_FUNC(PyObject*) _Py_wstrlist_as_pylist(
+    int len,
+    wchar_t **list);
+
+/* Py_GetArgcArgv() helpers */
+
+PyAPI_FUNC(void) _Py_ClearArgcArgv(void);
+PyAPI_FUNC(int) _Py_SetArgcArgv(int argc, wchar_t * const *argv);
+
+/* _PyCoreConfig */
+
 PyAPI_FUNC(_PyInitError) _PyCoreConfig_Read(_PyCoreConfig *config);
 PyAPI_FUNC(void) _PyCoreConfig_Clear(_PyCoreConfig *);
 PyAPI_FUNC(int) _PyCoreConfig_Copy(
@@ -26,6 +49,9 @@ PyAPI_FUNC(int) _PyCoreConfig_GetEnvDup(
     wchar_t **dest,
     wchar_t *wname,
     char *name);
+PyAPI_FUNC(_PyInitError) _PyCoreConfig_ReadFromArgv(_PyCoreConfig *config,
+    const _PyArgv *args);
+PyAPI_FUNC(void) _PyCoreConfig_Write(const _PyCoreConfig *config);
 
 #ifdef __cplusplus
 }

Include/internal/pycore_pathconfig.h

@@ -8,20 +8,6 @@ extern "C" {
 #  error "this header requires Py_BUILD_CORE or Py_BUILD_CORE_BUILTIN define"
 #endif
 
-PyAPI_FUNC(void) _Py_wstrlist_clear(
-    int len,
-    wchar_t **list);
-PyAPI_FUNC(wchar_t**) _Py_wstrlist_copy(
-    int len,
-    wchar_t **list);
-PyAPI_FUNC(_PyInitError) _Py_wstrlist_append(
-    int *len,
-    wchar_t ***list,
-    const wchar_t *str);
-PyAPI_FUNC(PyObject*) _Py_wstrlist_as_pylist(
-    int len,
-    wchar_t **list);
-
 typedef struct _PyPathConfig {
     /* Full path to the Python program */
     wchar_t *program_full_path;