cuvid: Support > 8bit input formats

Although cuvid can only output 8bit, it can consume HEVC Main10 if
the bit depth is set properly.

This requires a newer version of cuviddec.h from CUDA 8 (I expect),
although the CUDA 7.5 can be manually updated to enable it as well.

libavcodec/cuvid.c

@@ -157,6 +157,7 @@ static int CUDAAPI cuvid_handle_video_sequence(void *opaque, CUVIDEOFORMAT* form
     cuinfo.ulNumDecodeSurfaces = MAX_FRAME_COUNT;
     cuinfo.ulNumOutputSurfaces = 1;
     cuinfo.ulCreationFlags = cudaVideoCreate_PreferCUVID;
+    cuinfo.bitDepthMinus8 = format->bit_depth_luma_minus8;
 
     cuinfo.DeinterlaceMode = cudaVideoDeinterlaceMode_Weave;