Contiguous views also for Base.Slice

[tam724]

Besides Base.Colon base also uses Base.Slice to indicate complete slices of a dimension (https://github.com/JuliaLang/julia/blob/8fd607a7df9e65ed060c88f32d801c95aa8a573f/base/indices.jl#L382).
For views of GPUArrays, we can treat Slice the same way as Colon and create contiguous arrays (CuArray/.. etc) instead of SubArrays.

Closes JuliaGPU/CUDA.jl#2986

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diff --git a/test/testsuite/base.jl b/test/testsuite/base.jl
index 8a5ca85..f6bfd33 100644
--- a/test/testsuite/base.jl
+++ b/test/testsuite/base.jl
@@ -333,19 +333,19 @@ end
       end
 
       @test compare(x->view(x, :, 1:4, 3), AT, rand(Float32, 5, 4, 3))
-      @test compare(x->view(x, Base.Slice(Base.OneTo(5)), 1:4, 3), AT, rand(Float32, 5, 4, 3))
+        @test compare(x -> view(x, Base.Slice(Base.OneTo(5)), 1:4, 3), AT, rand(Float32, 5, 4, 3))
 
       let x = AT(rand(Float32, 5, 4, 3))
         @test_throws BoundsError view(x, :, :, 1:10)
       end
 
-      @testset "selectdim" begin
-        @test compare(x -> selectdim(x, 3, 1), AT, rand(Float32, 2, 2, 2))
-        let x = AT(rand(Float32, 5, 4, 3))
-          @test typeof(selectdim(x, 3, 1)) == typeof(view(x, :, :, 1))         
-          @test typeof(selectdim(x, 2, 1)) == typeof(view(x, :, 1, :))
+        @testset "selectdim" begin
+            @test compare(x -> selectdim(x, 3, 1), AT, rand(Float32, 2, 2, 2))
+            let x = AT(rand(Float32, 5, 4, 3))
+                @test typeof(selectdim(x, 3, 1)) == typeof(view(x, :, :, 1))
+                @test typeof(selectdim(x, 2, 1)) == typeof(view(x, :, 1, :))
+            end
         end
-      end
 
       # bug in parentindices conversion
       let x = AT{Int}(undef, 1, 1)