winks: Fix RGB frame flipping and postprocessing

winks: Fix RGB frame flipping and postprocessing

Uncompressed RGB frames can be (usually are) bottom-up
layout in DirectShow, and the code to flip them wasn't
properly ported from 0.10. Fix it.

Fix post-processing of RGB buffers. We need a writable
buffer, but the requests pool is holding an extra ref.
This could use more fixing to use a buffer pool