Merge r354164 from trunk:

Give a clue about what event really does, and some
small improvements to the leader and worker docs.

Submitted by: Noirin Plunkett <firebird nerdchic.net>, Joshua Slive



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@354167 13f79535-47bb-0310-9956-ffa450edef68