cloning array

[Alain De Vos]

```
import std.stdio;
void main(){
auto a=new int[][] (0,0);
a~=[1,2];
a~=[3,4];
auto b= a.dup;
a[0]=[5,6];
a[1][1]=7;
writeln(b);
}
```

Program above outputs [[1, 2], [3, 7]]
Which means a[1][1] and b[1][1] point to the same memory location.
But a[0] occupies a different memory location as b[0].
It is a shallow copy and is the expected behaviour.
Maybe there is need for a library function dupdeep ?