message: actually show warnings about suppressed output
diff: @@ -398,7 +398,7 @@ pub trait EvalContextExt<'a, 'mir, 'tcx: 'a+'mir>: crate::MiriEvalContextExt<'a,
  Err(_) => -1,
  }
  } else {
  - warn!("Ignored output to FD {}", fd);
  + eprintln!("Miri: Ignored output to FD {}", fd);
  n as i64 // pretend it all went well
  }; // now result is the value we return back to the program
  this.write_scalar(
  