Various Fix
 - Fix: master/buildbot/buildslave/manager.py
   - __repr__ method of BuildslaveRegistration
 - Fix: master/buildbot/process/buildrequest.py
   - new BuildRequest are now processed:
     - add self.master.mq.produce(('buildrequest', None, None, None, 'new'), dict(buildername=bn))
       (in order to wake up the BuildRequestDistributor activity_loop)
 - Fix: master/buildbot/process/buildrequest.py
   - set ss.patch to None instead of (None, None, None)
 - Fix: master/buildbot/status/buildstep.py
   - Make BuildStepStatus picklable