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/sync/src/chain/mod.rs

@@ -99,7 +99,7 @@ use std::time::{Duration, Instant};
 use hash::keccak;
 use heapsize::HeapSizeOf;
 use ethereum_types::{H256, U256};
-use plain_hasher::H256FastMap;
+use fastmap::H256FastMap;
 use parking_lot::RwLock;
 use bytes::Bytes;
 use rlp::{Rlp, RlpStream, DecoderError};

ethcore/sync/src/lib.rs

@@ -31,7 +31,7 @@ extern crate ethcore;
 extern crate ethereum_types;
 extern crate env_logger;
 extern crate hashdb;
-extern crate plain_hasher;
+extern crate fastmap;
 extern crate rand;
 extern crate semver;
 extern crate parking_lot;

ethcore/sync/src/transactions_stats.rs

@@ -17,7 +17,7 @@
 use api::TransactionStats;
 use std::collections::{HashSet, HashMap};
 use ethereum_types::{H256, H512};
-use plain_hasher::H256FastMap;
+use fastmap::H256FastMap;
 
 type NodeId = H512;
 type BlockNumber = u64;