Now supports multiple devices, and uses DirectSound 8 instead of 5. Changed
name to "directsound" and renamed source directory.

--HG--
rename : src/audio/windx5/SDL_dx5audio.c => src/audio/directsound/SDL_directsound.c
rename : src/audio/windx5/SDL_dx5audio.h => src/audio/directsound/SDL_directsound.h
rename : src/audio/windx5/directx.h => src/audio/directsound/directx.h