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> {
```

1 files changed, 3 insertions, 3 deletions

diff --git a/components/script/dom/bindings/js.rs b/components/script/dom/bindings/js.rs
index a0c099769f0..ac8da0f8ba6 100644
--- a/components/script/dom/bindings/js.rs
+++ b/components/script/dom/bindings/js.rs
@@ -51,7 +51,7 @@ use dom::node::Node;
 use js::jsapi::JSObject;
 use js::jsval::JSVal;
 use layout_interface::TrustedNodeAddress;
-use script_task::StackRoots;
+use script_task::STACK_ROOTS;
 
 use servo_util::smallvec::{SmallVec, SmallVec16};
 use std::cell::{Cell, UnsafeCell};
@@ -101,7 +101,7 @@ impl<T: Reflectable> Temporary<T> {
 
     /// Create a stack-bounded root for this value.
     pub fn root(self) -> Root<T> {
-        StackRoots.with(|ref collection| {
+        STACK_ROOTS.with(|ref collection| {
             let RootCollectionPtr(collection) = collection.get().unwrap();
             unsafe {
                 Root::new(&*collection, &self.inner)
@@ -164,7 +164,7 @@ impl<T: Reflectable> JS<T> {
 
     /// Root this JS-owned value to prevent its collection as garbage.
     pub fn root(&self) -> Root<T> {
-        StackRoots.with(|ref collection| {
+        STACK_ROOTS.with(|ref collection| {
             let RootCollectionPtr(collection) = collection.get().unwrap();
             unsafe {
                 Root::new(&*collection, self)