alloc_api::alloc::Alloc has been changed to AllocRef

[dbartussek]

• Discussion in the working group issue: Rename Alloc to AllocRef rust-lang/wg-allocators#8
• Rust pull request: Rename Alloc to AllocRef rust-lang/rust#68529

Currently one can see the difference between the traits by viewing the stable and nightly docs side by side:

• https://doc.rust-lang.org/std/alloc/trait.Alloc.html
• https://doc.rust-lang.org/nightly/std/alloc/trait.AllocRef.html

The main difference for this project seems to be that alloc now behaves nearly like the old alloc_excess function, returning both the pointer and allocated size.