Don't reexport bigint from util

ethcore/light/src/client/mod.rs

@@ -31,7 +31,9 @@ use ethcore::service::ClientIoMessage;
 use ethcore::encoded;
 use io::IoChannel;
 
-use util::{H256, U256, Mutex, RwLock};
+use bigint::prelude::U256;
+use bigint::hash::H256;
+use util::{Mutex, RwLock};
 use util::kvdb::{KeyValueDB, CompactionProfile};
 
 use self::header_chain::{AncestryIter, HeaderChain};