Fix fallout of removing default bounds

This is all purely fallout of getting the previous commit to compile.

src/libnative/io/pipe_unix.rs

@@ -150,8 +150,8 @@ impl rtio::RtioPipe for UnixStream {
         }
     }
 
-    fn clone(&self) -> ~rtio::RtioPipe {
-        ~UnixStream { inner: self.inner.clone() } as ~rtio::RtioPipe
+    fn clone(&self) -> ~rtio::RtioPipe:Send {
+        ~UnixStream { inner: self.inner.clone() } as ~rtio::RtioPipe:Send
     }
 }
 
@@ -250,8 +250,8 @@ impl UnixListener {
 }
 
 impl rtio::RtioUnixListener for UnixListener {
-    fn listen(~self) -> IoResult<~rtio::RtioUnixAcceptor> {
-        self.native_listen(128).map(|a| ~a as ~rtio::RtioUnixAcceptor)
+    fn listen(~self) -> IoResult<~rtio::RtioUnixAcceptor:Send> {
+        self.native_listen(128).map(|a| ~a as ~rtio::RtioUnixAcceptor:Send)
     }
 }
 
@@ -279,7 +279,7 @@ impl UnixAcceptor {
 }
 
 impl rtio::RtioUnixAcceptor for UnixAcceptor {
-    fn accept(&mut self) -> IoResult<~rtio::RtioPipe> {
-        self.native_accept().map(|s| ~s as ~rtio::RtioPipe)
+    fn accept(&mut self) -> IoResult<~rtio::RtioPipe:Send> {
+        self.native_accept().map(|s| ~s as ~rtio::RtioPipe:Send)
     }
 }