dirstate.walk: fast path match-always case during traversal This case is a common one -- e.g. `hg status`. For a repository with 170,000 files, this speeds up perfstatus --unknown from 2.15 seconds to 2.09.

largefiles: fix _always for match overrides Upcoming patches will speed dirstate.walk up by not filtering based on the match function when match.always() is True. For that to work, match.always() needs to be accurate. Previously it wasn't so for largefiles.