Don't block sync when importing old blocks (#8530)

* Alter IO queueing.

* Don't require IoMessages to be Clone

* Ancient blocks imported via IoChannel.

* Get rid of private transactions io message.

* Get rid of deadlock and fix disconnected handler.

* Revert to old disconnect condition.

* Fix tests.

* Fix deadlock.

ethcore/src/views/block.rs

@@ -29,7 +29,6 @@ pub struct BlockView<'a> {
 	rlp: ViewRlp<'a>
 }
 
-
 impl<'a> BlockView<'a> {
 	/// Creates new view onto block from rlp.
 	/// Use the `view!` macro to create this view in order to capture debugging info.
@@ -39,9 +38,9 @@ impl<'a> BlockView<'a> {
 	/// ```
 	/// #[macro_use]
 	/// extern crate ethcore;
-	/// 
+	///
 	/// use ethcore::views::{BlockView};
-	/// 
+	///
 	/// fn main() {
 	/// let bytes : &[u8] = &[];
 	/// let block_view = view!(BlockView, bytes);