vdpau: remove old-style decoders

Signed-off-by: Anton Khirnov <anton@khirnov.net>
vdpau: deprecate old codec-specific pixel formats

Signed-off-by: Anton Khirnov <anton@khirnov.net>
vdpau: deprecate VDPAU codec capability

Signed-off-by: Anton Khirnov <anton@khirnov.net>
vdpau: store picture data in picture's rather than codec's context

Signed-off-by: Anton Khirnov <anton@khirnov.net>
vdpau: deprecate bitstream buffers within the hardware context

The bitstream buffers are now private and freed by libavcodec. For
backward compatibility, the hold bitstream buffer pointer is left NULL
(applications were supposed to av_freep() it).

Signed-off-by: Anton Khirnov <anton@khirnov.net>