  o Minor bugfixes (testing, compilation):
    - Refrain from trying to get an item from empty smartlist in
      test_bridges_clear_bridge_list. Set DEBUG_SMARTLIST in unit
      tests to catch improper smartlist usage. Furthermore,
      enable DEBUG_SMARTLIST globally when build is configured
      with fragile hardening. Fixes bug 26196; bugfix on
      0.3.4.1-alpha.
