auto merge of #4575 : mttr/servo/warnings, r=jdm

Notes:

* This adds `#![allow(missing_copy_implementations)]` to components/*/lib.rs. I'm not sure how to approach the missing Copy warnings (are there things for which Copy should NOT be implemented, and how can I tell?) so I stuck this in to make life easier when looking through the warnings. I can easily remove this if necessary. 
* This leaves the following type of warnings, which I couldn't figure out how to approach (I'll investigate it later if no one else wants to).
```
css/matching.rs:72:23: 72:35 warning: use of deprecated item: Use overloaded core::cmp::PartialEq, #[warn(deprecated)] on by default
css/matching.rs:72         this_as_query.equiv(other)
                                         ^~~~~~~~~~~~
css/matching.rs:95:10: 95:49 warning: use of deprecated item: Use overloaded core::cmp::PartialEq, #[warn(deprecated)] on by default
css/matching.rs:95 impl<'a> Equiv<ApplicableDeclarationsCacheEntry> for ApplicableDeclarationsCacheQuery<'a> {
```

components/layout/context.rs

@@ -28,10 +28,10 @@ struct LocalLayoutContext {
     style_sharing_candidate_cache: StyleSharingCandidateCache,
 }
 
-thread_local!(static local_context_key: Cell<*mut LocalLayoutContext> = Cell::new(ptr::null_mut()))
+thread_local!(static LOCAL_CONTEXT_KEY: Cell<*mut LocalLayoutContext> = Cell::new(ptr::null_mut()))
 
 fn create_or_get_local_context(shared_layout_context: &SharedLayoutContext) -> *mut LocalLayoutContext {
-    local_context_key.with(|ref r| {
+    LOCAL_CONTEXT_KEY.with(|ref r| {
         if r.get().is_null() {
             let context = box LocalLayoutContext {
                 font_context: FontContext::new(shared_layout_context.font_cache_task.clone()),

components/layout/layout_debug.rs

@@ -14,7 +14,7 @@ use std::cell::RefCell;
 use std::io::File;
 use std::sync::atomic::{AtomicUint, SeqCst, INIT_ATOMIC_UINT};
 
-thread_local!(static state_key: RefCell<Option<State>> = RefCell::new(None))
+thread_local!(static STATE_KEY: RefCell<Option<State>> = RefCell::new(None))
 
 static mut DEBUG_ID_COUNTER: AtomicUint = INIT_ATOMIC_UINT;
 
@@ -59,7 +59,7 @@ struct State {
 /// will be output at the beginning and end of this scope.
 impl Scope {
     pub fn new(name: String) -> Scope {
-        state_key.with(|ref r| {
+        STATE_KEY.with(|ref r| {
             match &mut *r.borrow_mut() {
                 &Some(ref mut state) => {
                     let flow_trace = json::encode(&flow::base(state.flow_root.deref()));
@@ -76,7 +76,7 @@ impl Scope {
 #[cfg(not(ndebug))]
 impl Drop for Scope {
     fn drop(&mut self) {
-        state_key.with(|ref r| {
+        STATE_KEY.with(|ref r| {
             match &mut *r.borrow_mut() {
                 &Some(ref mut state) => {
                     let mut current_scope = state.scope_stack.pop().unwrap();
@@ -100,9 +100,9 @@ pub fn generate_unique_debug_id() -> u16 {
 /// Begin a layout debug trace. If this has not been called,
 /// creating debug scopes has no effect.
 pub fn begin_trace(flow_root: FlowRef) {
-    assert!(state_key.with(|ref r| r.borrow().is_none()));
+    assert!(STATE_KEY.with(|ref r| r.borrow().is_none()));
 
-    state_key.with(|ref r| {
+    STATE_KEY.with(|ref r| {
         let flow_trace = json::encode(&flow::base(flow_root.deref()));
         let state = State {
             scope_stack: vec![box ScopeData::new("root".into_string(), flow_trace)],
@@ -116,7 +116,7 @@ pub fn begin_trace(flow_root: FlowRef) {
 /// trace to disk in the current directory. The output
 /// file can then be viewed with an external tool.
 pub fn end_trace() {
-    let mut task_state = state_key.with(|ref r| r.borrow_mut().take().unwrap());
+    let mut task_state = STATE_KEY.with(|ref r| r.borrow_mut().take().unwrap());
     assert!(task_state.scope_stack.len() == 1);
     let mut root_scope = task_state.scope_stack.pop().unwrap();
     root_scope.post = json::encode(&flow::base(task_state.flow_root.deref()));

components/layout/lib.rs

@@ -7,6 +7,7 @@
 #![deny(unused_imports)]
 #![deny(unused_variables)]
 #![allow(unrooted_must_root)]
+#![allow(missing_copy_implementations)]
 
 #[phase(plugin, link)]
 extern crate log;