&[1, 2, 3] should always be &'static [<generic integer>]

The following works:

``` rust
fn foo<'a>(xs: &'a [int]) -> &'a [int] {
    if xs.len() & 1 == 0 {
        static ys: &'static [int] = &[1, 2, 3];
        ys
    } else {
        xs
    }
}
```

This should also work, but does not:

``` rust
fn foo<'a>(xs: &'a [int]) -> &'a [int] {
    if xs.len() & 1 == 0 {
        &[1, 2, 3]
    } else {
        xs
    }
}
```
