Introduce better hashing.

- Blake2 for secure hashing
- XX for fast hashing

substrate/state_machine/Cargo.toml

@@ -7,7 +7,6 @@ description = "Polkadot State Machine"
 [dependencies]
 polkadot-primitives = { path = "../primitives", version = "0.1.0" }
 hashdb = "0.1.1"
-keccak-hash = "0.1.0"
 patricia-trie = "0.1.0"
 memorydb = "0.1.1"
 triehash = "0.1"

substrate/state_machine/src/lib.rs

@@ -22,7 +22,6 @@ extern crate polkadot_primitives as primitives;
 
 extern crate hashdb;
 extern crate memorydb;
-extern crate keccak_hash;
 
 extern crate patricia_trie;
 extern crate triehash;