Actually remove libc dependency.

Author: SSheldon

Cargo.toml

@@ -11,6 +11,3 @@ documentation = "http://ssheldon.github.io/rust-objc/dispatch/"
 license = "MIT"
 
 exclude = [".gitignore"]
-
-[dependencies]
-libc = ">= 0.1, < 0.3"

src/lib.rs

@@ -44,8 +44,6 @@ assert!(nums[0] == "2");
 
 #![warn(missing_docs)]
 
-extern crate libc;
-
 use std::cell::UnsafeCell;
 use std::ffi::{CStr, CString};
 use std::mem;