fsmonitor: refresh pywatchman to upstream
Update to upstream to version c77452. The refresh includes fixes to improve
windows compatibility.
There is a minor update to 'test-check-py3-compat.t' as c77452 no longer have
the py3 compatibility issues the previous version had.
# no-check-commit
Our full contribution guidelines are in our wiki, please see:
https://www.mercurial-scm.org/wiki/ContributingChanges
If you just want a checklist to follow, you can go straight to
https://www.mercurial-scm.org/wiki/ContributingChanges#Submission_checklist
If you can't run the entire testsuite for some reason (it can be
difficult on Windows), please at least run `contrib/check-code.py` on
any files you've modified and run `python contrib/check-commit` on any
commits you've made (for example, `python contrib/check-commit
273ce12ad8f1` will report some style violations on a very old commit).