bpo-35059: Convert PyObject_INIT() to function (GH-10077)

* Convert PyObject_INIT() and PyObject_INIT_VAR() macros to static
  inline functions.
* Fix usage of these functions: cast to PyObject* or PyVarObject*.
diff --git a/PC/winreg.c b/PC/winreg.c
index 78864b1..4f5a676 100644
--- a/PC/winreg.c
+++ b/PC/winreg.c
@@ -459,7 +459,7 @@
     op = (PyHKEYObject *) PyObject_MALLOC(sizeof(PyHKEYObject));
     if (op == NULL)
         return PyErr_NoMemory();
-    PyObject_INIT(op, &PyHKEY_Type);
+    PyObject_INIT((PyObject *)op, &PyHKEY_Type);
     op->hkey = h;
     return (PyObject *)op;
 }