added __all__ lists to a number of Python modules

added test script and expected output file as well
this closes patch 103297.
__all__ attributes will be added to other modules without first submitting
a patch, just adding the necessary line to the test script to verify
more-or-less correct implementation.

Lib/cmd.py

@@ -37,6 +37,8 @@ they automatically support Emacs-like command history and editing features.
 
 import string
 
+__all__ = ["Cmd"]
+
 PROMPT = '(Cmd) '
 IDENTCHARS = string.letters + string.digits + '_'