Make HashDB generic (#8739)

The `patricia_trie` crate is generic over the hasher (by way of HashDB) and node encoding scheme. Adds a new `patricia_trie_ethereum` crate with concrete impls for Keccak/RLP.

ethcore/src/json_tests/executive.rs

@@ -31,7 +31,7 @@ use ethjson;
 use trace::{Tracer, NoopTracer};
 use trace::{VMTracer, NoopVMTracer};
 use bytes::{Bytes, BytesRef};
-use trie;
+use ethtrie;
 use rlp::RlpStream;
 use hash::keccak;
 use machine::EthereumMachine as Machine;
@@ -93,7 +93,7 @@ impl<'a, T: 'a, V: 'a, B: 'a> TestExt<'a, T, V, B>
 		address: Address,
 		tracer: &'a mut T,
 		vm_tracer: &'a mut V,
-	) -> trie::Result<Self> {
+	) -> ethtrie::Result<Self> {
 		let static_call = false;
 		Ok(TestExt {
 			nonce: state.nonce(&address)?,

ethcore/src/json_tests/trie.rs

@@ -16,8 +16,10 @@
 
 use ethjson;
 use trie::{TrieFactory, TrieSpec};
+use ethtrie::RlpCodec;
 use ethereum_types::H256;
 use memorydb::MemoryDB;
+use keccak_hasher::KeccakHasher;
 
 use super::HookType;
 
@@ -28,13 +30,13 @@ pub use self::secure::run_test_file as run_secure_test_file;
 
 fn test_trie<H: FnMut(&str, HookType)>(json: &[u8], trie: TrieSpec, start_stop_hook: &mut H) -> Vec<String> {
 	let tests = ethjson::trie::Test::load(json).unwrap();
-	let factory = TrieFactory::new(trie);
+	let factory = TrieFactory::<_, RlpCodec>::new(trie);
 	let mut result = vec![];
 
 	for (name, test) in tests.into_iter() {
 		start_stop_hook(&name, HookType::OnStart);
 
-		let mut memdb = MemoryDB::new();
+		let mut memdb = MemoryDB::<KeccakHasher>::new();
 		let mut root = H256::default();
 		let mut t = factory.create(&mut memdb, &mut root);