futures: tests/sink_fanout.rs: Don't break w/o features
Symbols/Imports pushed down / localised
Tests gated with cfg()
Tests now build and pass with all valid feature combinations
See previous commits for details and rationale
+#[cfg(all(feature = "alloc", feature="std", feature="executor"))] // channel::mpsc, executor::
+#[test]
+fn it_works() {
use futures::channel::mpsc;
use futures::executor::block_on;
use futures::future::join3;
use futures::sink::SinkExt;
use futures::stream::{self, StreamExt};
-#[test]
-fn it_works() {
let (tx1, rx1) = mpsc::channel(1);
let (tx2, rx2) = mpsc::channel(2);
let tx = tx1.fanout(tx2).sink_map_err(|_| ());
