Add async-routes test for #[get] and #[catch].

core/codegen/tests/async-routes.rs

@@ -0,0 +1,19 @@
+#![feature(proc_macro_hygiene)]
+
+#[macro_use] extern crate rocket;
+use rocket::http::uri::Origin;
+use rocket::request::Request;
+
+async fn noop() { }
+
+#[get("/")]
+async fn hello(_origin: &Origin<'_>) -> &'static str {
+    noop().await;
+    "Hello, world!"
+}
+
+#[catch(404)]
+async fn not_found(req: &Request<'_>) -> String {
+    noop().await;
+    format!("{} not found", req.uri())
+}