Remove unused extern crates.

examples/load_elf.rs

@@ -5,7 +5,6 @@
 // copied, modified, or distributed except according to those terms.
 
 
-extern crate byteorder;
 extern crate elf;
 use std::path::PathBuf;
 

examples/to_json.rs

@@ -8,7 +8,6 @@
 #[macro_use]
 extern crate json;
 
-extern crate byteorder;
 extern crate elf;
 use std::path::PathBuf;
 

src/lib.rs

@@ -20,7 +20,6 @@
 use std::u32;
 use std::collections::HashMap;
 
-extern crate libc;
 extern crate combine;
 extern crate time;