Non-mixing decoding in SMPEG...

[Ryan C. Gordon]

...I'm going to implement this, but I want to make sure I know the correct
way to tackle this.

I want to have SMPEG _not_ mix when decoding audio into a memory buffer,
avoiding the SDL_MixAudio() overhead and such.

Is the best way to handle this:

1) To add a function like SMPEG_SetMixingPolicy(true/false), and use the
rest of the functions as normal, or
2) To add a function like SMPEG_DecodeWithoutMixing(blah), and not touch
the rest of the codebase.

Obviously, the names will be different.  :)

Thoughts?

--ryan.