bpo-22257: Private C-API for main interpreter initialization (PEP 432). (#1729)

(patch by Nick Coghlan)
diff --git a/Include/pylifecycle.h b/Include/pylifecycle.h
index f1a19c1..0d609ec 100644
--- a/Include/pylifecycle.h
+++ b/Include/pylifecycle.h
@@ -23,7 +23,8 @@
 /* PEP 432 Multi-phase initialization API (Private while provisional!) */
 PyAPI_FUNC(void) _Py_InitializeCore(const _PyCoreConfig *);
 PyAPI_FUNC(int) _Py_IsCoreInitialized(void);
-PyAPI_FUNC(int) _Py_InitializeMainInterpreter(int install_sigs);
+PyAPI_FUNC(int) _Py_ReadMainInterpreterConfig(_PyMainInterpreterConfig *);
+PyAPI_FUNC(int) _Py_InitializeMainInterpreter(const _PyMainInterpreterConfig *);
 #endif
 
 /* Initialization and finalization */