Add dependency on multiboot2 crate

Cargo.toml

@@ -10,3 +10,4 @@ crate-type = ["staticlib"]
 rlibc = "1.0"
 volatile = "0.1.0"
 spin = "0.4.5"
+multiboot2 = "0.1.0"

src/lib.rs

@@ -7,6 +7,7 @@
 extern crate rlibc;
 extern crate volatile;
 extern crate spin;
+extern crate multiboot2;
 
 #[macro_use]
 mod vga_buffer;