SDL windows audio test

The SDL DirectSound code has been updated, hopefully addressing the audio
quality problems on Windows. If you’ve been having troubles, please try
the DLL snapshot available here:
If there are any audio dropouts detected, they will be written to stderr.txt

If you have problems running that, or want to play with the source, you
can grab it and define DEBUG_SOUND when you build it:

Please let me know what the results are for you.

-Sam Lantinga, Senior Software Engineer, Blizzard Entertainment