Because the pollset is now only mutated from the event thread, we no longer...

Because the pollset is now only mutated from the event thread, we no longer need the APR_POLLSET_THREADSAFE flag for the event_pollset


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1202258 13f79535-47bb-0310-9956-ffa450edef68