rustfmt adds newlines after block comments

With `normalize_comments` set to `false`, running rustfmt can lead to extra newlines being placed.

Here is some example code:

``` rust
fn test() {
    let a = 5;
    // A comment
    /*let b = 6;
    let c = 7;*/

    let d = 5;
}
```

Everytime rustfmt is run on this code, a newline is placed above `let d = 5;`.
