Update to 1.877
    
    - New upstream release 1.877
      - Improved suppressing the PDL CLONE warning; piddles should not be naively
        copied into new threads
      - Added fast channel implementations optimized for non-Unicode strings:
        - MCE::Channel::MutexFast
        - MCE::Channel::SimpleFast
        - MCE::Channel::ThreadsFast
        The main difference is that these lack freeze-thaw serialization