Added ind2sub(::AbstractArray, ::Integer)

As per request https://github.com/JuliaLang/julia/issues/294#issuecomment-65828607 
Not sure what you want me to do here.  I am all for changing int() to Int(), my own Julia types work that way, too, I think that makes more sense.  

But this PR is only about a small addition to ind2sub()---mainly because for NamedArrays the interpretation can be: give names of indices rather than integer indices.  For that, I need the array itself, not just the size.