Pavane - The draft version of the newer version of abc can be found on the abc Home page at abc-draft.txt
You might also look at The abc plus project which has implementations of some of these new features.
While you're on the abc Home Page, if you're in the mood you might also look at the Beethoven 7th work for use of some extensions to abc.
I'm off to Bruges now - I'll check this thread out again when I get back. (Or if you want to e-mail me use MCPearce0ATaolDOTcom - that's a zero before AT)