FLAC decoder (and a playsound.c bug)

[Ryan C. Gordon]

> With a big, scary deadline looming at work, I haven't had the time or
> the energy to do much with SDL_sound. I hope this will change now that
> the deadline is gone (but not forgotten).

I've been pretty overwhelmed recently, too. I got about halfway through a
ADPCM-compressed .WAV decoder a few weeks (!) ago, and never had a chance
to get back to it. I will soon, though.

> But only approximately. I was getting an annoying ticking sound
> throughout the whole playback, which I think I've finally tracked down
> to a bug in playsound.c. (Perhaps we ought to leave the playsound bug a
> bit longer because I managed to simplify flac.c a bit while searching
> there for the bug. ;-)

Sorry, I'm committing the playsound.c patch.  :) This actually fixed an
.OGG problem I was having, too, so it's very handy.

I put some more comments into the audio callback in addition to your
patch, but I still feel like it's pretty sloppy. I want to reorganize it,
but I know that I always manage to break it when I touch it, so I'm
holding off for now.  :)

I'm going to go install libFLAC and then I'll commit the flac module, too.

--ryan.