Host validation (again) (#1666)

* Revert "Revert "Validating Host headers in RPC requests" (#1663)"

This reverts commit 3cc3dbef66.

* Fixing binding on MacOS

dapps/src/lib.rs

@@ -129,6 +129,7 @@ impl Server {
 			special.insert(router::SpecialEndpoint::Utils, apps::utils());
 			special
 		});
+		let bind_address = format!("{}", addr);
 
 		try!(hyper::Server::http(addr))
 			.handle(move |_| router::Router::new(
@@ -136,6 +137,7 @@ impl Server {
 				endpoints.clone(),
 				special.clone(),
 				authorization.clone(),
+				bind_address.clone(),
 			))
 			.map(|(l, srv)| {