tests/test-fuzz-targets.t

py3: add b'' prefixes in tests/test-custom-filters.t

# skip-blame because just b'' prefixes

Differential Revision: https://phab.mercurial-scm.org/D3595

#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