Update to 1.881 (rhbz#2134723)
    
    - New upstream release 1.881 (rhbz#2134723)
      - Improved the private _parse_chunk_size function for better utilization of
        CPU cores in MCE::Grep, MCE::Map, and MCE::Stream, processing small input
        sizes
        - Previously, chunk_size => 'auto' equals 2 minimally
        - Starting with MCE v1.881, 'auto' equals 1 minimally