changelog: also monitor `00changelog.n` when applicable (
issue6554)
This let the locarepo's file cache detect outdated nodemap docket and reload the
changelog after `localrepo.invalidate` when applicable.
Differential Revision: https://phab.mercurial-scm.org/D11482
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init
$ echo 'base' > base
$ hg ci -Ambase
adding base
$ hg qnew -mmqbase mqbase
$ hg qsave
$ hg qrestore 2
restoring status: hg patches saved state