cv::cuda::merge not support 6 channel

[williamlzw]

cv::cuda::GpuMat channels[6] = { d_mat1, d_mat2, d_mat3, d_mat4, d_mat5, d_mat6 };
cv::cuda::merge(channels, 6, image);

void mergeImpl(const GpuMat* src, size_t n, cv::OutputArray _dst, Stream& stream)
{
CV_Assert( src != 0 );
CV_Assert( n > 0 && n <= 4 );//======================

[cudawarped]

I think this is more of a feature request than a bug. The "bug" would be that the documentation should be updated to indicate that this only works with up to four channels i.e. not GpuMatND.