Split Server::listen into two methods to hack around ICE related to default type params

Trying to default the type parameters leads to an ICE and strange type errors.
I think this is just due to the experimental state of default type params and
this change can be rolled back when they are fixed.

benches/client.rs

@@ -8,9 +8,8 @@ extern crate test;
 use std::fmt::{mod, Show};
 use std::io::net::ip::Ipv4Addr;
 use hyper::server::{Incoming, Server};
-use hyper::net::HttpAcceptor;
 
-fn listen() -> hyper::server::Listening<HttpAcceptor> {
+fn listen() -> hyper::server::Listening {
     let server = Server::http(Ipv4Addr(127, 0, 0, 1), 0);
     server.listen(handle).unwrap()
 }
@@ -70,11 +69,11 @@ fn bench_hyper(b: &mut test::Bencher) {
         let mut req = hyper::get(hyper::Url::parse(url).unwrap()).unwrap();
         req.headers.set(Foo);
 
-        req
-            .send().unwrap()
-            .read_to_string().unwrap()
+    req
+        .send().unwrap()
+        .read_to_string().unwrap()
     });
-    listening.close().unwrap()
+listening.close().unwrap()
 }
 
 #[bench]