Remove things specific to the old Macintosh, and spell "Mac OS X" consistently.
diff --git a/Doc/using/cmdline.rst b/Doc/using/cmdline.rst
index 94fbed7..4ceee84 100644
--- a/Doc/using/cmdline.rst
+++ b/Doc/using/cmdline.rst
@@ -516,7 +516,7 @@
 
    If this environment variable is set, ``sys.argv[0]`` will be set to its
    value instead of the value got through the C runtime.  Only works on
-   MacOS X.
+   Mac OS X.
 
 
 Debug-mode variables