test-check-help: fix to work on Windows The initial problem was `hg files` prints paths with '\', which gets removed when piped (scanhelptopics.py failed to open 'hgext__init__.py'). Then, xargs was invoking `hg help` with 'backout\r (esc)', which setting binary mode prevents.

branchmap: be more careful about using %d on ints Not doing so breaks Python 3.