Pin types have moved

[Arnavion]

rust-lang/rust#53227

 --> C:\Users\Arnavion\.cargo\registry\src\github.com-1ecc6299db9ec823\futures-core-preview-0.3.0-alpha.3\src\future.rs:4:5
  |
4 | use core::mem::PinMut;
  |     ^^^^^^^^^^^^^^^^^ no `PinMut` in `mem`

error[E0432]: unresolved import `core::mem::PinMut`
 --> C:\Users\Arnavion\.cargo\registry\src\github.com-1ecc6299db9ec823\futures-core-preview-0.3.0-alpha.3\src\stream.rs:5:5
  |
5 | use core::mem::PinMut;
  |     ^^^^^^^^^^^^^^^^^ no `PinMut` in `mem`

error[E0603]: struct `PinBox` is private
   --> C:\Users\Arnavion\.cargo\registry\src\github.com-1ecc6299db9ec823\futures-core-preview-0.3.0-alpha.3\src\stream.rs:128:27
    |
128 |     use std::boxed::{Box, PinBox};
    |                           ^^^^^^

[Arnavion]

Already being fixed by #1231