std: Modernize the local_data api

This commit brings the local_data api up to modern rust standards with a few key
improvements:

* The `pop` and `set` methods have been combined into one method, `replace`

* The `get_mut` method has been removed. All interior mutability should be done
  through `RefCell`.

* All functionality is now exposed as a method on the keys themselves. Instead
  of importing std::local_data, you now use "key.replace()" and "key.get()".

* All closures have been removed in favor of RAII functionality. This means that
  get() and get_mut() no long require closures, but rather return
  Option<SmartPointer> where the smart pointer takes care of relinquishing the
  borrow and also implements the necessary Deref traits

* The modify() function was removed to cut the local_data interface down to its
  bare essentials (similarly to how RefCell removed set/get).

[breaking-change]

1 files changed, 4 insertions, 5 deletions

diff --git a/src/libstd/rt/task.rs b/src/libstd/rt/task.rs
index 5b29de5a8c1..68d8c446cf9 100644
--- a/src/libstd/rt/task.rs
+++ b/src/libstd/rt/task.rs
@@ -414,13 +414,12 @@ mod test {
 
     #[test]
     fn tls() {
-        use local_data;
         local_data_key!(key: @~str)
-        local_data::set(key, @"data".to_owned());
-        assert!(*local_data::get(key, |k| k.map(|k| *k)).unwrap() == "data".to_owned());
+        key.replace(Some(@"data".to_owned()));
+        assert_eq!(key.get().unwrap().as_slice(), "data");
         local_data_key!(key2: @~str)
-        local_data::set(key2, @"data".to_owned());
-        assert!(*local_data::get(key2, |k| k.map(|k| *k)).unwrap() == "data".to_owned());
+        key2.replace(Some(@"data".to_owned()));
+        assert_eq!(key2.get().unwrap().as_slice(), "data");
     }
 
     #[test]