Updates to SDL_sound

[Torbjörn Andersson]

Ryan C. Gordon wrote:

 > Sam seems to think that SDL_endian.h should NOT be included in SDL.h,
 > which doesn't make any sense to me, but oh well.

Actually, what I meant was that aiff.c will get SDL_endian.h through 
SDL_sound.h, but perhaps that was always the case. I can't remember now 
why I explicitly included SDL_endian.h into aiff.c. I'd like to think 
there was some terribly good reason, but... :-)

Torbjörn Andersson