Literals don't have static lifetime

OK:
```rust
fn get_slice_ok() -> &'static [u8] {
    const CONST: &'static [u8] = &[0];
    CONST
}
```
Borrowck error:
```rust
fn get_slice_error() -> &'static [u8] {
    &[0]
}
```
But consts and literals are basically the same thing, so I'd expect this to work.