message: fix(common): Don't use reserved byte position
diff: @@ -160,7 +160,7 @@ impl SourceMap {
  ) -> SourceMap {
  SourceMap {
  files: Default::default(),
  - start_pos: Default::default(),
  + start_pos: AtomicUsize::new(1),
  file_loader,
  path_mapping,
  doctest_offset: None,
  