Update to 2018 edition

Cargo.toml

 [package]
 name = "uefi_alloc"
 version = "0.1.0"
+edition = "2018"
 
 [dependencies]
 uefi = { git = "https://gitlab.redox-os.org/redox-os/uefi.git" }

src/lib.rs

@@ -3,8 +3,6 @@
 #![feature(try_trait)]
 #![no_std]
 
-extern crate uefi;
-
 use core::alloc::{GlobalAlloc, Layout};
 use core::ops::Try;
 use core::ptr;