* switch --resultlog to --junit-xml in testrunner/runner.py, lib_python_tests.py,
  pypyjit_tests.py, and buildbot/bot2/pypybuildbot/builds.py; rewrite
  should_report_failure() in runner.py to detect crashes by checking for a
  valid XML testsuite rather than resultlog F/E/P lines; drop -p resultlog and
  the RemovedInPytest4Warning filter from pytest.ini
* find a better way to run "find" without creating the index storage,
  if one is not already readily available (understand cost now, improve after merge)
* improve performance of splitlines
* think about cost of utf8 list strategy (Armin and CF)
