match: make _donormalize's auditor and warn arguments optional
Argument 'warn' is actually non-required, since there's a 'if warn:'
check before usage. Argument 'auditor' is passed to
pathutil.canonpath(), in which it is optional.
To run the tests, do:
cd tests/
python run-tests.py
See https://mercurial-scm.org/wiki/WritingTests for
more information on writing tests.