Remove io::LocalOutput and use Arc<Mutex<dyn>> for local streams.

library/std/src/io/impls.rs

@@ -209,20 +209,6 @@ impl<B: BufRead + ?Sized> BufRead for Box<B> {
     }
 }
 
-// Used by panicking::default_hook
-#[cfg(test)]
-/// This impl is only used by printing logic, so any error returned is always
-/// of kind `Other`, and should be ignored.
-impl Write for dyn ::realstd::io::LocalOutput {
-    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
-        (*self).write(buf).map_err(|_| ErrorKind::Other.into())
-    }
-
-    fn flush(&mut self) -> io::Result<()> {
-        (*self).flush().map_err(|_| ErrorKind::Other.into())
-    }
-}
-
 // =============================================================================
 // In-memory buffer implementations