Call practracker as part of check-local.

- 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.

scripts/maint/practracker/problem.py

@@ -96,6 +96,6 @@ def get_old_problem_from_exception_str(exception_str):
     elif problem_type == "function-size":
         return FunctionSizeProblem(problem_location, metric_value)
     else:
-        print("Unknown exception line {}".format(exception_str))
+#        print("Unknown exception line '{}'".format(exception_str))
         return None