cuvid: Don't wait for vp8/9 AR frames

Alternate Reference frames never appear in the output - they are
purely used as references. As such, do not increment the wait
counter when you get one, as you'll never see it on the other side.

Note that this change requires cuviddec.h to be fixed up according
to the Video SDK header - cuda 7.5's header is missing the vp8
block and the vp9 block is simply wrong.

libavcodec/cuvid.c

@@ -221,7 +221,13 @@ static int CUDAAPI cuvid_handle_picture_decode(void *opaque, CUVIDPICPARAMS* pic
 
     av_log(avctx, AV_LOG_TRACE, "pfnDecodePicture\n");
 
-    if (ctx->deint_mode == cudaVideoDeinterlaceMode_Weave)
+    if (ctx->cuparseinfo.CodecType == cudaVideoCodec_VP9 &&
+        !picparams->CodecSpecific.vp9.showFrame) {
+        // An AR frame. Don't wait for it.
+    } else if (ctx->cuparseinfo.CodecType == cudaVideoCodec_VP8 &&
+               !picparams->CodecSpecific.vp8.show_frame) {
+        // An AR frame. Don't wait for it.
+    } else if (ctx->deint_mode == cudaVideoDeinterlaceMode_Weave)
         ctx->waiting_frames += 1;
     else
         ctx->waiting_frames += 2;