sys/directsound/gstdirectsoundsink.*: Remove include of unused headers.

sys/directsound/gstdirectsoundsink.*: Remove include of unused headers.

Original commit message from CVS:
* sys/directsound/gstdirectsoundsink.c:
* sys/directsound/gstdirectsoundsink.h:
Remove include of unused headers.
* sys/waveform/gstwaveformplugin.c:
* sys/waveform/gstwaveformsink.c:
* sys/waveform/gstwaveformsink.h:
* win32/vs6/libgstwaveform.dsp:
Add a new waveform plugin which includes an audio sink
element using the WaveForm win32 API.
* win32/MANIFEST:
Add the new project file form waveform plugin.