Override deepcopy, not deepcopy_internal, to avoid invalidations.

Closes #632.

Author: IanButterworth

src/array.jl

@@ -408,7 +408,10 @@ function Base.unsafe_copyto!(dest::DenseCuArray{T}, doffs, src::DenseCuArray{T},
   return dest
 end
 
-function Base.deepcopy_internal(x::CuArray, dict::IdDict)
+# XXX: defining deepcopy_internal, as per the deepcopy documentation, results in a ton
+#      of invalidations, so we redefine deepcopy itself (see JuliaGPU/CUDA.jl#632)
+function Base.deepcopy(x::CuArray)
+  dict = IdDict()
   haskey(dict, x) && return dict[x]::typeof(x)
   return dict[x] = copy(x)
 end