Move ethereum-specific H256FastMap type to own crate (#9307)

* Add a `fastmap` crate that provides the H256FastMap specialized HashMap

* Use `fastmap` instead of `plain_hasher`

* Update submodules for Reasons™

* Submodule update

ethcore/light/src/client/header_chain.rs

@@ -41,7 +41,7 @@ use ethereum_types::{H256, H264, U256};
 use heapsize::HeapSizeOf;
 use kvdb::{DBTransaction, KeyValueDB};
 use parking_lot::{Mutex, RwLock};
-use plain_hasher::H256FastMap;
+use fastmap::H256FastMap;
 use rlp::{Encodable, Decodable, DecoderError, RlpStream, Rlp};
 use smallvec::SmallVec;
 

ethcore/light/src/lib.rs

@@ -68,7 +68,7 @@ extern crate keccak_hasher;
 extern crate memorydb;
 extern crate patricia_trie as trie;
 extern crate patricia_trie_ethereum as ethtrie;
-extern crate plain_hasher;
+extern crate fastmap;
 extern crate rand;
 extern crate rlp;
 extern crate parking_lot;

ethcore/light/src/transaction_queue.rs

@@ -29,7 +29,7 @@ use std::collections::hash_map::Entry;
 
 use transaction::{self, Condition, PendingTransaction, SignedTransaction};
 use ethereum_types::{H256, U256, Address};
-use plain_hasher::H256FastMap;
+use fastmap::H256FastMap;
 
 // Knowledge of an account's current nonce.
 #[derive(Debug, Clone, PartialEq, Eq)]