Add a dependency on the x86_64 crate

Cargo.toml

@@ -12,3 +12,4 @@ volatile = "0.1.0"
 spin = "0.4.5"
 multiboot2 = "0.1.0"
 bitflags = "0.7.0"
+x86_64 = "0.1.2"

src/lib.rs

@@ -10,6 +10,7 @@ extern crate spin;
 extern crate multiboot2;
 #[macro_use]
 extern crate bitflags;
+extern crate x86_64;
 
 #[macro_use]
 mod vga_buffer;