patch 8.1.1291: not easy to change directory and restore

Problem:    Not easy to change directory and restore.
Solution:   Add the chdir() function. (Yegappan Lakshmanan, closes #4358)
diff --git a/src/if_py_both.h b/src/if_py_both.h
index ede2f5c..498972d 100644
--- a/src/if_py_both.h
+++ b/src/if_py_both.h
@@ -1032,7 +1032,7 @@
     Py_DECREF(newwd);
     Py_XDECREF(todecref);
 
-    post_chdir(FALSE, FALSE);
+    post_chdir(CDSCOPE_GLOBAL);
 
     if (VimTryEnd())
     {