Update for latest nightly changes

Author: bjorn3

src/main.rs

@@ -10,6 +10,7 @@ compile_error!("The bootloader crate must be compiled for the `x86_64-bootloader
 extern crate rlibc;
 
 use bootloader::bootinfo::{BootInfo, FrameRange};
+use core::arch::asm;
 use core::convert::TryInto;
 use core::panic::PanicInfo;
 use core::{mem, slice};