Indexing with arrays

This is with CuArrays own indexing disabled.

Strangely plain arrays seem to work, but not cuarrays.

```
julia> cu([1:5;])[[5,2,3]]
3-element CuArray{Float32,1}:
 5.0
 2.0
 3.0

julia> cu([1:5;])[cu[5,2,3]]
ERROR: scalar getindex is disabled
```