[beta] Using pending block only if is not old (#2515)

* Using pending block only if not old

Conflicts:
	ethcore/src/miner/miner.rs
	rpc/src/v1/impls/eth.rs
	rpc/src/v1/impls/eth_filter.rs

* Fixing compilation issues

ethcore/src/client/client.rs

@@ -1036,7 +1036,7 @@ impl BlockChainClient for Client {
 	}
 
 	fn pending_transactions(&self) -> Vec<SignedTransaction> {
-		self.miner.pending_transactions()
+		self.miner.pending_transactions(self.chain.best_block_number())
 	}
 }
 

ethcore/src/client/test_client.rs

@@ -558,6 +558,6 @@ impl BlockChainClient for TestBlockChainClient {
 	}
 
 	fn pending_transactions(&self) -> Vec<SignedTransaction> {
-		self.miner.pending_transactions()
+		self.miner.pending_transactions(self.chain_info().best_block_number)
 	}
 }