Support multiple interpreters.

Author: serhiy-storchaka

Modules/imathmodule.c

@@ -1277,21 +1277,26 @@ static PyMethodDef imath_methods[] = {
     {NULL,              NULL}           /* sentinel */
 };
 
+static PyModuleDef_Slot imath_slots[] = {
+    {Py_mod_multiple_interpreters, Py_MOD_PER_INTERPRETER_GIL_SUPPORTED},
+    {Py_mod_gil, Py_MOD_GIL_NOT_USED},
+    {0, NULL}
+};
 
 PyDoc_STRVAR(module_doc,
 "This module provides access to integer related mathematical functions.");
 
-
 static struct PyModuleDef imathmodule = {
     PyModuleDef_HEAD_INIT,
     .m_name = "imath",
     .m_doc = module_doc,
     .m_size = 0,
     .m_methods = imath_methods,
+    .m_slots = imath_slots,
 };
 
 PyMODINIT_FUNC
 PyInit_imath(void)
 {
-    return PyModule_Create(&imathmodule);
+    return PyModuleDef_Init(&imathmodule);
 }