Fixed bugs:
- Fix a case when CPU cores > 128(MAX_NUM_THREADS) / 3 (#319).
- Avoid dis-filtering ref when not needed, fix return type (#325).
- Update name of file for failed dis_path fopen (#334).
- A few compilation fixes (warnings and errors) (#326).
- Bump up g++ version to 9 for travis (#352).
- Use stat struct instead of ftell to retrieve the file size (#350).
New features: