Remove old features 'clone_from_slice' and 'convert'

components/canvas/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/. */
 
-#![feature(clone_from_slice)]
 #![feature(nonzero)]
 #![feature(plugin)]
 #![plugin(plugins)]

components/compositing/lib.rs

@@ -3,7 +3,6 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #![feature(box_syntax)]
-#![feature(clone_from_slice)]
 #![feature(custom_derive)]
 #![feature(plugin)]
 #![feature(mpsc_select)]

components/gfx/lib.rs

@@ -3,7 +3,6 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // For simd (currently x86_64/aarch64)
-#![cfg_attr(any(target_arch = "x86_64", target_arch = "aarch64"), feature(convert))]
 #![cfg_attr(any(target_os = "linux", target_os = "android", target_os = "windows"), feature(heap_api))]
 
 #![feature(alloc)]