Fix warnings: unnecessary mut

ethcore/src/client/client.rs

@@ -302,7 +302,7 @@ impl Importer {
         ) = {
             let mut imported_blocks = Vec::with_capacity(max_blocks_to_import);
             let mut invalid_blocks = HashSet::new();
-            let mut proposed_blocks = Vec::with_capacity(max_blocks_to_import);
+            let proposed_blocks = Vec::with_capacity(max_blocks_to_import);
             let mut import_results = Vec::with_capacity(max_blocks_to_import);
 
             let _import_lock = self.import_lock.lock();

ethcore/src/engines/clique/mod.rs

@@ -294,7 +294,7 @@ impl Clique {
 						"Back-filling block state. last_checkpoint_number: {}, target: {}({}).",
 						last_checkpoint_number, header.number(), header.hash());
 
-                let mut chain: &mut VecDeque<Header> = &mut VecDeque::with_capacity(
+                let chain: &mut VecDeque<Header> = &mut VecDeque::with_capacity(
                     (header.number() - last_checkpoint_number + 1) as usize,
                 );
 

ethcore/src/ethereum/ethash.rs

@@ -308,7 +308,7 @@ impl Engine<EthereumMachine> for Arc<Ethash> {
                 let n_uncles = block.uncles.len();
 
                 // Bestow block rewards.
-                let mut result_block_reward = reward + reward.shr(5) * U256::from(n_uncles);
+                let result_block_reward = reward + reward.shr(5) * U256::from(n_uncles);
 
                 rewards.push((author, RewardKind::Author, result_block_reward));
 

ethcore/src/json_tests/executive.rs

@@ -325,7 +325,7 @@ fn do_json_test_for<H: FnMut(&str, HookType)>(
                 &mut tracer,
                 &mut vm_tracer,
             ));
-            let mut evm = vm_factory.create(params, &schedule, 0);
+            let evm = vm_factory.create(params, &schedule, 0);
             let res = evm
                 .exec(&mut ex)
                 .ok()