Fix Linux build

Author: petrochenkov

src/libstd/sys/unix/net.rs

@@ -14,7 +14,6 @@ use ffi::CStr;
 use io;
 use libc::{self, c_int, size_t, sockaddr, socklen_t};
 use net::{SocketAddr, Shutdown};
-use str;
 use sys::fd::FileDesc;
 use sys_common::{AsInner, FromInner, IntoInner};
 use sys_common::net::{getsockopt, setsockopt};

src/libstd/sys/unix/os.rs

@@ -26,7 +26,6 @@ use memchr;
 use path::{self, PathBuf};
 use ptr;
 use slice;
-use str;
 use sync::StaticMutex;
 use sys::cvt;
 use sys::fd;