DMA support for ALSA driver

I’ve written an SDL audio driver called alsadma which uses DMA instead
of read/write with ALSA.

The work in progress is at
http://www.skynet.ie/~airlied/patches/sdl/sdl_alsadma.diff

and is against current CVS.

It isn’t finished, and probably needs a lot of work on error handling…

Just throwiing it out there as I’ve a few other things to do and might
not get back to it for a while…

Dave.