Auto merge of #17493 - froydnj:rust-117-fixes, r=jdm

remove various things now that Rust 1.17 is required

std::ptr::eq and Arc::ptr_eq are now usuable, and we can replace a
panic!() with abort().

- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes do not require tests because they are trivial replacements.

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/17493)
<!-- Reviewable:end -->

components/style/lib.rs

@@ -186,14 +186,6 @@ macro_rules! reexport_computed_values {
 }
 longhand_properties_idents!(reexport_computed_values);
 
-/// Pointer equality
-///
-/// FIXME: Remove this and use std::ptr::eq once we require Rust 1.17
-#[inline]
-pub fn ptr_eq<T: ?Sized>(a: *const T, b: *const T) -> bool {
-    a == b
-}
-
 /// Serializes as CSS a comma-separated list of any `T` that supports being
 /// serialized as CSS.
 pub fn serialize_comma_separated_list<W, T>(dest: &mut W,

components/style/shared_lock.rs

@@ -10,6 +10,8 @@ use atomic_refcell::{AtomicRefCell, AtomicRef, AtomicRefMut};
 use parking_lot::RwLock;
 use std::cell::UnsafeCell;
 use std::fmt;
+#[cfg(feature = "gecko")]
+use std::ptr;
 use stylearc::Arc;
 
 /// A shared read/write lock that can protect multiple objects.
@@ -154,7 +156,7 @@ impl<T> Locked<T> {
 
     #[cfg(feature = "gecko")]
     fn same_lock_as(&self, derefed_guard: &SomethingZeroSizedButTyped) -> bool {
-        ::ptr_eq(self.shared_lock.cell.as_ptr(), derefed_guard)
+        ptr::eq(self.shared_lock.cell.as_ptr(), derefed_guard)
     }
 
     /// Access the data for reading.