doc: add more doc_cfg annotations (#1821)

Also makes the `tokio::net::{tcp, udp, unix}` modules only for "utility"
types. The primary types are in `tokio::net` directly.

1 files changed, 5 insertions, 3 deletions

diff --git a/tokio/src/net/unix/listener.rs b/tokio/src/net/unix/listener.rs
index 7791b05f..5f4787ec 100644
--- a/tokio/src/net/unix/listener.rs
+++ b/tokio/src/net/unix/listener.rs
@@ -12,9 +12,11 @@ use std::os::unix::net::{self, SocketAddr};
 use std::path::Path;
 use std::task::{Context, Poll};
 
-/// A Unix socket which can accept connections from other Unix sockets.
-pub struct UnixListener {
-    io: PollEvented<mio_uds::UnixListener>,
+cfg_uds! {
+    /// A Unix socket which can accept connections from other Unix sockets.
+    pub struct UnixListener {
+        io: PollEvented<mio_uds::UnixListener>,
+    }
 }
 
 impl UnixListener {