message: Use Deadlock machine stop uniformly
diff: @@ -352,9 +352,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
  let readers = rwlock_get_readers(this, rwlock_op)?.to_u32()?;
  let writers = rwlock_get_writers(this, rwlock_op)?.to_u32()?;
  if writers != 0 {
  - throw_unsup_format!(
  - "Deadlock due to read-locking a pthreads read-write lock while it is already write-locked"
  - );
  + throw_machine_stop!(TerminationInfo::Deadlock);
  } else {
  match readers.checked_add(1) {
  Some(new_readers) => {
  @@ -390,13 +388,9 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
  let readers = rwlock_get_readers(this, rwlock_op)?.to_u32()?;
  let writers = rwlock_get_writers(this, rwlock_op)?.to_u32()?;
  if readers != 0 {
  - throw_unsup_format!(
  - "Deadlock due to write-locking a pthreads read-write lock while it is already read-locked"
  - );
  + throw_machine_stop!(TerminationInfo::Deadlock);
  } else if writers != 0 {
  - throw_unsup_format!(
  - "Deadlock due to write-locking a pthreads read-write lock while it is already write-locked"
  - );
  + throw_machine_stop!(TerminationInfo::Deadlock);
  } else {
  rwlock_set_writers(this, rwlock_op, Scalar::from_u32(1))?;
  Ok(0)
  