Use PyThreadState_DeleteCurrent() instead of PyThreadState_Delete()
and PyEval_ReleaseThread().

This fixes SF bug #125673 PyThreadState_Delete: invalid tstate (Unix
only?).
diff --git a/Modules/threadmodule.c b/Modules/threadmodule.c
index e0afde5..48f1f36 100644
--- a/Modules/threadmodule.c
+++ b/Modules/threadmodule.c
@@ -204,8 +204,7 @@
 	else
 		Py_DECREF(res);
 	PyThreadState_Clear(tstate);
-	PyEval_ReleaseThread(tstate);
-	PyThreadState_Delete(tstate);
+	PyThreadState_DeleteCurrent();
 	PyThread_exit_thread();
 }