image and object attributes in lang spec need work

The writeup in the lang spec for the image and object attributes 
doesn't reflect what I sent Don and Michael last March--unfortunately,
it looks like I never sent my text to the list, but just to Don
and Michael:
http://lists.oasis-open.org/archives/dita/200603/msg00016.html
Sorry about that.

Attached to this message is what I sent out last March--the lang
spec should be updated to reflect this.

paul