Simplify and clean up the embedded main import code to make it work how it's...

Simplify and clean up the embedded main import code to make it work how it's officially supposed to work: use the inittab.

Cython/Utility/Embed.c

@@ -26,32 +26,23 @@ static int __Pyx_main(int argc, wchar_t **argv) {
 #endif
     if (argc && argv)
         Py_SetProgramName(argv[0]);
+
+    #if PY_MAJOR_VERSION < 3
+    if (PyImport_AppendInittab("%(module_name)s", init%(module_name)s) < 0) return 1;
+    #else
+    if (PyImport_AppendInittab("%(module_name)s", PyInit_%(module_name)s) < 0) return 1;
+    #endif
+
     Py_Initialize();
     if (argc && argv)
         PySys_SetArgv(argc, argv);
+
     { /* init module '%(module_name)s' as '__main__' */
       PyObject* m = NULL;
       %(module_is_main)s = 1;
-      #if PY_MAJOR_VERSION < 3
-          init%(module_name)s();
-      #elif CYTHON_PEP489_MULTI_PHASE_INIT
-          m = PyInit_%(module_name)s();
-          if (!PyModule_Check(m)) {
-              PyModuleDef *mdef = (PyModuleDef *) m;
-              PyObject *modname = PyUnicode_FromString("__main__");
-              m = NULL;
-              if (modname) {
-                  // FIXME: not currently calling PyModule_FromDefAndSpec() here because we do not have a module spec!
-                  // FIXME: not currently setting __file__, __path__, __spec__, ...
-                  m = PyModule_NewObject(modname);
-                  Py_DECREF(modname);
-                  if (m) PyModule_ExecDef(m, mdef);
-              }
-          }
-      #else
-          m = PyInit_%(module_name)s();
-      #endif
-      if (PyErr_Occurred()) {
+      m = PyImport_ImportModule("%(module_name)s");
+
+      if (!m && PyErr_Occurred()) {
           PyErr_Print(); /* This exits with the right code if SystemExit. */
           #if PY_MAJOR_VERSION < 3
           if (Py_FlushLine()) PyErr_Clear();