Add workaround for flush&seek problems with certain formats

With some formats like VC-1, calling VPU_DecFlushAll() causes the decoder
to eventually fail for unknown reasons -> do not flush for these

Signed-off-by: Carlos Rafael Giani <dv@pseudoterminal.org>
Cleanup framedropping notes

Signed-off-by: Carlos Rafael Giani <dv@pseudoterminal.org>
Missed todo entry about motion JPEG encoder

Signed-off-by: Carlos Rafael Giani <dv@pseudoterminal.org>