Operator for pass by move

[Per Nordlöw]

Have anybody considered dedicating a specific operator for 
pass-by-move semantics in assignments and argument passing?

For instance,

```d
y = x;
z = f(y);
```

copies `x` and `y` whereas

```d
y = <<x;
z = f(<<y);
```

moves `x` and `y`.