use similar when possible

`similar` creates the same array type instead of the hard-coded
Array. This can be useful to support for instance CuArray.

src/extreme_filter.jl

@@ -349,7 +349,7 @@ function _extreme_filter_C4_2D!(
 
     #creating temporaries
     ySize, xSize = size(A)
-    tmp = Array{T,1}(undef, ySize)
+    tmp = similar(out, eltype(out), ySize)
     tmp2 = similar(tmp)
 
     # applying radius=r filter is equivalent to applying radius=1 filter r times