Instead of excluding directories at the last minute if they happen
to appear in our filenames, we exclude them early, before recursing
into all their subdirectories.
Part of 29746.
This was causing issues because the exceptions file is written using Posix
paths, whereas practracker in Windows was trying to match Windows paths ("\"
instead of "/").
- Introduce 'make check-best-practices'.
- Fix up Tor topdir etc to work with the way 'make check-local' gets called.
- Make practracker less likely to print useless stuff.
