[Playlist] new draft

[Lucas Gonze]

See http://gonze.com/xspf/xspf.org/xspf-v1.html for a proposed version 
containing all the revisions I have posted about today.  Please post 
related suggestions sooner rather than later.

A diff is available on request.  I wouldn't recommend it, though -- 
there are too many small changes for the diff to be readable.

This version includes all the changes that have been suggested recently, 
except for Sebastien's proposed changes to the TOC.  Those are slow and 
picky to implement and I ran out of time in the weekend.

-Lucas