sshpeer: make pipe polling code more explicit "hasbuffer" is a property on our special bufferedinputpipe class. When reading this code, I thought it might have had something special to do properties on built-in types. But "hasbuffer" doesn't appear in the CPython code base for either 2.7 or 3.7, so the answer is no. Let's make the code more explicit about the fact that it deals with our special bufferedinputpipe type. Differential Revision: https://phab.mercurial-scm.org/D2382

#require clang-libfuzzer test-repo
  $ cd $TESTDIR/../contrib/fuzz
  $ make
Just run the fuzzer for five seconds to verify it works at all.
  $ ./bdiff -max_total_time 5