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, 3 insertions, 6 deletions

diff --git a/src/liblog/lib.rs b/src/liblog/lib.rs
index 035a81f4143..09e9cd83f3d 100644
--- a/src/liblog/lib.rs
+++ b/src/liblog/lib.rs
@@ -122,7 +122,6 @@ use std::cast;
 use std::fmt;
 use std::io::LineBufferedWriter;
 use std::io;
-use std::local_data;
 use std::os;
 use std::rt;
 use std::slice;
@@ -228,7 +227,7 @@ pub fn log(level: u32, loc: &'static LogLocation, args: &fmt::Arguments) {
     // Completely remove the local logger from TLS in case anyone attempts to
     // frob the slot while we're doing the logging. This will destroy any logger
     // set during logging.
-    let mut logger = local_data::pop(local_logger).unwrap_or_else(|| {
+    let mut logger = local_logger.replace(None).unwrap_or_else(|| {
         box DefaultLogger { handle: io::stderr() } as Box<Logger:Send>
     });
     logger.log(&LogRecord {
@@ -238,7 +237,7 @@ pub fn log(level: u32, loc: &'static LogLocation, args: &fmt::Arguments) {
         module_path: loc.module_path,
         line: loc.line,
     });
-    local_data::set(local_logger, logger);
+    local_logger.replace(Some(logger));
 }
 
 /// Getter for the global log level. This is a function so that it can be called
@@ -250,9 +249,7 @@ pub fn log_level() -> u32 { unsafe { LOG_LEVEL } }
 /// Replaces the task-local logger with the specified logger, returning the old
 /// logger.
 pub fn set_logger(logger: Box<Logger:Send>) -> Option<Box<Logger:Send>> {
-    let prev = local_data::pop(local_logger);
-    local_data::set(local_logger, logger);
-    return prev;
+    local_logger.replace(Some(logger))
 }
 
 /// A LogRecord is created by the logging macros, and passed as the only