Remove unneeded extern crates and imports

(backport <rust-lang#3897>)
(cherry picked from commit ba1b27f)

Author: eduardosm

libc-test/build.rs

@@ -1,6 +1,5 @@
 #![deny(warnings)]
 
-extern crate cc;
 extern crate ctest2 as ctest;
 
 use std::fs::File;

libc-test/test/cmsg.rs

@@ -1,8 +1,6 @@
 //! Compare libc's CMSG(3) family of functions against the actual C macros, for
 //! various inputs.
 
-extern crate libc;
-
 #[cfg(unix)]
 mod t {
 

libc-test/test/errqueue.rs

@@ -1,7 +1,5 @@
 //! Compare libc's SO_EE_OFFENDER function against the actual C macro
 
-extern crate libc;
-
 #[cfg(any(target_os = "linux", target_os = "android"))]
 mod t {
     use libc::{self, sock_extended_err, sockaddr};

libc-test/test/linux_elf.rs

@@ -1,6 +1,5 @@
 #![allow(bad_style, improper_ctypes, unused, deprecated)]
 
-extern crate libc;
 use libc::*;
 
 #[cfg(target_os = "linux")]

libc-test/test/linux_fcntl.rs

@@ -1,6 +1,5 @@
 #![allow(bad_style, improper_ctypes, unused, deprecated)]
 
-extern crate libc;
 use libc::*;
 
 #[cfg(any(target_os = "linux", target_os = "android"))]

libc-test/test/linux_if_arp.rs

@@ -1,6 +1,5 @@
 #![allow(bad_style, improper_ctypes, unused, deprecated)]
 
-extern crate libc;
 use libc::*;
 
 #[cfg(any(target_os = "linux", target_os = "android"))]

libc-test/test/linux_ipv6.rs

@@ -1,6 +1,5 @@
 #![allow(bad_style, improper_ctypes, unused, deprecated)]
 
-extern crate libc;
 use libc::*;
 
 #[cfg(target_os = "linux")]

libc-test/test/linux_kernel_version.rs

@@ -1,7 +1,5 @@
 //! Compare libc's KERNEL_VERSION macro against a specific kernel version.
 
-extern crate libc;
-
 #[cfg(
     target_os = "linux",
 )]

libc-test/test/linux_strerror_r.rs

@@ -1,6 +1,5 @@
 #![allow(bad_style, improper_ctypes, unused, deprecated)]
 
-extern crate libc;
 use libc::*;
 
 #[cfg(any(target_os = "linux", target_os = "android"))]

libc-test/test/linux_termios.rs

@@ -1,6 +1,5 @@
 #![allow(bad_style, improper_ctypes, unused, deprecated)]
 
-extern crate libc;
 use libc::*;
 
 #[cfg(any(target_os = "linux", target_os = "android"))]