try! -> ?

Automated conversion using the untry tool [1] and the following command:

```
$ find -name '*.rs' -type f | xargs untry
```

at the root of the Rust repo.

[1]: https://github.com/japaric/untry

src/libstd/panic.rs

@@ -315,7 +315,7 @@ pub fn recover<F: FnOnce() -> R + RecoverSafe, R>(f: F) -> Result<R> {
     let mut result = None;
     unsafe {
         let result = &mut result;
-        try!(unwind::try(move || *result = Some(f())))
+        unwind::try(move || *result = Some(f()))?
     }
     Ok(result.unwrap())
 }