I need some help for my DCV update

[Ferhat Kurtulmuş]

I am working on the DCV to make it compilable with the recent 
versions of LDC, mir libraries, and stuff. I have not yet simply 
forked it to work on it. I am including modules one by one for my 
convenience instead. Hope, I am close to the end. Here is my 
temporary repo:

https://github.com/aferust/ddcv

I run into some problems with module convolution, especially the 
function conv invoked by the below code which calls canny edge 
filter:
```
Image image = imread("lena.png");
auto slice = image.sliced.rgb2gray;
//auto equalized = 
slice.histEqualize(slice.flattened.calcHistogram);

slice.asImage.imshow("Original");
auto edge = slice.canny!ubyte(15);
edge.asImage.imshow("edge");
waitKey();
```
Somehow, the compiler fails in deducting the types. I need some 
help from Ilya or other people familiar with mir.ndslice.

To reproduce it, download my repo and try to compile it as it is. 
There is a main with the test code in the repo. Just be sure you 
have a glfw3.dll/.so.

```
source\dcv\imgproc\filter.d(547,18): Error: template 
`dcv.imgproc.convolution.conv` cannot deduce function from 
argument types `!()(Slice!(ubyte*, 2LU, 
mir_slice_kind.contiguous), Slice!(float*, 2LU, 
mir_slice_kind.contiguous), Slice!(float*, 2LU, 
mir_slice_kind.contiguous), Slice!(float*, 2LU, 
mir_slice_kind.contiguous), TaskPool)`
source\dcv\imgproc\filter.d(548,18): Error: template 
`dcv.imgproc.convolution.conv` cannot deduce function from 
argument types `!()(Slice!(ubyte*, 2LU, mir_sut, KernelTensor 
kerlice_kind.contiguous), Slice!(float*, 2LU, 
mir_slice_kind.contiguous), Slice!(float*, 2LU, 
mir_slice_kind.contiguous), Slice!(float*, 2LU, 
mir_slice_kind.contiguous), TaskPool)`                            
                                                                   
                                            lice_kind.contiguous
source\dcv\imgproc\convolution.d(78,13):        Candidate is: 
`conv(alias bc = neumann, InputTensor, KernelTensor, MaskTensor = 
KernelTensor)(InputTensor input, KernelTensor kernel, InputTensor 
prealloc = InputTensor.init, MaskTensor mask = MaskTensor.init, 
TaskPool pool = taskPool)`                              ut, 
KernelTensor ker
source\dcv\imgproc\filter.d(674,18): Error: template instance 
`dcv.imgproc.filter.calcGradients!(Slice!(ubyte*, 2LU, 
mir_slice_kind.contiguous), float)` error instantiating           
                                                                   
                                                                  
r instantiating
source\dcv\imgproc\filter.d(694,24):        instantiated from 
here: `canny!(ubyte, ubyte, mir_slice_kind.contiguous)`
source\app.d(48,34):        instantiated from here: 
`canny!(ubyte, ubyte, mir_slice_kind.contiguous)`
```

I tried explicitly passing template parameters in 
dcv.imgproc.filter.calcGradients like below, but in that way, I 
am getting some other compilation errors:
```
alias Empty2Type = Slice!(V*, 2LU, SliceKind.contiguous);
fx = input.conv(neumann, typeof(input), Empty2Type, Empty2Type)
     (kx, emptySlice!(2LU, V), emptySlice!(2LU, V), pool);
fy = input.convinput.conv(neumann, typeof(input), Empty2Type, 
Empty2Type)
      (ky, emptySlice!(2LU, V), emptySlice!(2LU, V), pool);
```

Thanks in advance!