setup: add hgext.lfs to list of Python packages
This is needed for lfs to get installed. Probably could stand to go
into an earlier patch, but I just want to get this stuff pushed.
Set up
$ hg init repo
$ cd repo
Try to import an empty patch
$ hg import --no-commit - <<EOF
> EOF
applying patch from stdin
abort: stdin: no diffs found
[255]
No dirstate backups are left behind
$ ls .hg/dirstate* | sort
.hg/dirstate