[kvdb-memorydb] Migrated code to 2018 edition, updated parking_lot (#222

)

* Migrated code to 2018 edition, updated parking_lot

* revert parking_lot update due to breakages

kvdb-memorydb/Cargo.toml

@@ -1,10 +1,11 @@
 [package]
 name = "kvdb-memorydb"
-version = "0.1.0"
+version = "0.1.1"
 authors = ["Parity Technologies <admin@parity.io>"]
 repository = "https://github.com/paritytech/parity-common"
 description = "A key-value in-memory database that implements the  `KeyValueDB` trait"
 license = "GPL-3.0"
+edition = "2018"
 
 [dependencies]
 parking_lot = "0.6"

kvdb-memorydb/src/lib.rs

@@ -14,11 +14,7 @@
 // You should have received a copy of the GNU General Public License
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.
 
-extern crate parking_lot;
-extern crate kvdb;
-
-use std::collections::{BTreeMap, HashMap};
-use std::io;
+use std::{io, collections::{BTreeMap, HashMap}};
 use parking_lot::RwLock;
 use kvdb::{DBValue, DBTransaction, KeyValueDB, DBOp};
 
@@ -87,7 +83,7 @@ impl KeyValueDB for InMemory {
 		Ok(())
 	}
 
-	fn iter<'a>(&'a self, col: Option<u32>) -> Box<Iterator<Item=(Box<[u8]>, Box<[u8]>)> + 'a> {
+	fn iter<'a>(&'a self, col: Option<u32>) -> Box<dyn Iterator<Item=(Box<[u8]>, Box<[u8]>)> + 'a> {
 		match self.columns.read().get(&col) {
 			Some(map) => Box::new( // TODO: worth optimizing at all?
 				map.clone()
@@ -99,7 +95,7 @@ impl KeyValueDB for InMemory {
 	}
 
 	fn iter_from_prefix<'a>(&'a self, col: Option<u32>, prefix: &'a [u8])
-		-> Box<Iterator<Item=(Box<[u8]>, Box<[u8]>)> + 'a>
+		-> Box<dyn Iterator<Item=(Box<[u8]>, Box<[u8]>)> + 'a>
 	{
 		match self.columns.read().get(&col) {
 			Some(map) => Box::new(