std: Fix fallout of changing #[deriving(Clone)]

Author: Jorge Aparicio

src/libstd/collections/hash/set.rs

@@ -10,7 +10,6 @@
 //
 // ignore-lexer-test FIXME #15883
 
-use clone::Clone;
 use cmp::{Eq, Equiv, PartialEq};
 use core::kinds::Sized;
 use default::Default;

src/libstd/io/process.rs

@@ -26,7 +26,6 @@ use rt::rtio;
 use c_str::CString;
 use collections::HashMap;
 use hash::Hash;
-use clone::Clone;
 #[cfg(windows)]
 use std::hash::sip::SipState;