[SDL] 1.3 availability date

[Ryan C. Gordon]

> Speaking of 1.3, I have a very hard time understanding the new driver
> organization to port 1.2 drivers.

The video stuff is totally different, and I can't really speak about it 
with authority right now, but my understanding is that the backends 
aren't ported to it so much as rewritten for it.

I've moved most of the 1.2 audio backends to the 1.3 API at this 
point...the last few are either being removed or are on my TODO list.

--ryan.