Notable changes:
 - Converters between types are autogenerated. Instead of making multiple
   passes over the data with seperate filters for endianess, size, signedness,
   etc, converting between data types is always one specialized filter. This
   simplifies SDL_BuildAudioCVT(), which otherwise had a million edge cases
   with the new types, and makes the actually conversions more CPU cache
   friendly. Left a stub for adding specific optimized versions of these
   routines (SSE/MMX/Altivec, assembler, etc)
 - Autogenerated converters are built by SDL/src/audio/sdlgenaudiocvt.pl. This
   does not need to be run unless tweaking the code, and thus doesn't need
   integration into the build system.
 - Went through all the drivers and tried to weed out all the "Uint16"
   references that are better specified with the new SDL_AudioFormat typedef.
 - Cleaned out a bunch of hardcoded bitwise magic numbers and replaced them
   with new SDL_AUDIO_* macros.
 - Added initial float32 and int32 support code. Theoretically, existing
   drivers will push these through converters to get the data they want to
   feed to the hardware.

Still TODO:
 - Optimize and debug new converters.
 - Update the CoreAudio backend to accept float32 data directly.
 - Other backends, too?
 - SDL_LoadWAV() needs to be updated to support int32 and float32 .wav files
   (both of which exist and can be generated by 'sox' for testing purposes).
 - Update the mixer to handle new datatypes.
 - Optionally update SDL_sound and SDL_mixer, etc.

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%402029