The patch looks OK (except for some minor cosmetic changes I would
apply).

My only problem with it is your copyright notice. AFAIK, patches to the
Python core cannot contain copyright notices without proper license
information. OTOH, I don't think that these minor changes really warrant
adding a complete license paragraph.

Wouldn't a line like 
"Additional changes to support decoding maps by Martin v. Loewis" suffice ?
Which changes these are would be immediately clear by looking at the
CVS history.