shill: add ability to blacklist devices

BUG=chromium-os:16787
TEST=ebuild + manual

manual testing: set up mac80211_hwsim and hostapd on a device.
run shill, observe that it core dumps. run shill again, with
"--black-list=mon.wlan1", observe that it does not core dump.

Change-Id: Id43ed8badc2d8ac414c8a2ceb7487ecb85dc851c
Reviewed-on: http://gerrit.chromium.org/gerrit/4414
Reviewed-by: mukesh agrawal <quiche@chromium.org>
Tested-by: mukesh agrawal <quiche@chromium.org>
diff --git a/manager.h b/manager.h
index 839e7fe..b784cdf 100644
--- a/manager.h
+++ b/manager.h
@@ -43,6 +43,8 @@
           EventDispatcher *dispatcher,
           GLib *glib);
   virtual ~Manager();
+
+  void AddDeviceToBlackList(const std::string &device_name);
   void Start();
   void Stop();