Rust: properly highlight lifetime specifiers
Rust: properly highlight lifetime specifiers

Like in this snippet:

```
fn foo<'a, 'bbb>(a: &'a int, bb: &'bbb int) -> char {
    'x'
}
```

kirbyfan64/pygments-unofficial,kirbyfan64/pygments-unofficial,kirbyfan64/pygments-unofficial,kirbyfan64/pygments-unofficial,kirbyfan64/pygments-unofficial,kirbyfan64/pygments-unofficial,kirbyfan64/pygments-unofficial,kirbyfan64/pygments-unofficial,kirbyfan64/pygments-unofficial,kirbyfan64/pygments-unofficial,kirbyfan64/pygments-unofficial,kirbyfan64/pygments-unofficial,kirbyfan64/pygments-unofficial,kirbyfan64/pygments-unofficial,kirbyfan64/pygments-unofficial,kirbyfan64/pygments-unofficial