Rename Alloc to AllocRef

Required to land rust-lang/rust#68529. Please see that PR for details. The CI is expected to fail until the PR is landed.

Author: TimDiekmann

tests/run-pass/heap_allocator.rs

@@ -1,10 +1,10 @@
 #![feature(allocator_api)]
 
 use std::ptr::NonNull;
-use std::alloc::{Global, Alloc, Layout, System};
+use std::alloc::{Global, AllocRef, Layout, System};
 use std::slice;
 
-fn check_alloc<T: Alloc>(mut allocator: T) { unsafe {
+fn check_alloc<T: AllocRef>(mut allocator: T) { unsafe {
     for &align in &[4, 8, 16, 32] {
         let layout = Layout::from_size_align(20, align).unwrap();
 
@@ -40,7 +40,7 @@ fn check_alloc<T: Alloc>(mut allocator: T) { unsafe {
     }
 } }
 
-fn check_align_requests<T: Alloc>(mut allocator: T) {
+fn check_align_requests<T: AllocRef>(mut allocator: T) {
     for &size in &[2, 8, 64] { // size less than and bigger than alignment
         for &align in &[4, 8, 16, 32] { // Be sure to cover less than and bigger than `MIN_ALIGN` for all architectures
             let iterations = 32;