Based on a patch by Ron Yorston.

This reverts commit fdfff7cf.

In theory, this commit should have had no affect on winmm-using
applications and just prevented underruns on the mmdevapi side. But
Patrol Falcon abuses the winmm API by modifying the buffer after
passing it to waveOutWrite, and this patch breaks that behavior. We've
improved the winecoreaudio driver since this patch was sent, and so
large buffers should no longer be necessary to avoid underruns.