Use the packed_simd crate instead of std::simd

`std::simd` was removed in https://github.com/rust-lang/rust/pull/52535.
https://crates.io/crates/packed_simd is in the rust-lang-nursery org.

components/gfx/Cargo.toml

@@ -13,7 +13,7 @@ test = false
 doctest = false
 
 [features]
-unstable = []
+unstable = ["packed_simd"]
 
 [dependencies]
 app_units = "0.6"
@@ -30,6 +30,7 @@ log = "0.4"
 malloc_size_of = { path = "../malloc_size_of" }
 net_traits = {path = "../net_traits"}
 new-ordered-float = "1.0"
+packed_simd = {version = "0.1", optional = true}
 range = {path = "../range"}
 serde = "1.0"
 servo_arc = {path = "../servo_arc"}

components/gfx/lib.rs

@@ -2,7 +2,6 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-#![cfg_attr(feature = "unstable", feature(stdsimd))]
 #![deny(unsafe_code)]
 
 extern crate app_units;
@@ -43,6 +42,8 @@ extern crate log;
 extern crate malloc_size_of;
 extern crate net_traits;
 extern crate ordered_float;
+#[cfg(all(feature = "unstable", any(target_feature = "sse2", target_feature = "neon")))]
+extern crate packed_simd;
 extern crate range;
 #[macro_use] extern crate serde;
 extern crate servo_arc;

components/gfx/text/glyph.rs

@@ -4,11 +4,11 @@
 
 use app_units::Au;
 use euclid::Point2D;
+#[cfg(all(feature = "unstable", any(target_feature = "sse2", target_feature = "neon")))]
+use packed_simd::u32x4;
 use range::{self, EachIndex, Range, RangeIndex};
 use std::{fmt, mem, u16};
 use std::cmp::{Ordering, PartialOrd};
-#[cfg(all(feature = "unstable", any(target_feature = "sse2", target_feature = "neon")))]
-use std::simd::u32x4;
 use std::vec::Vec;
 
 pub use gfx_traits::ByteIndex;