Merge r1544629, r1544626 from trunk:

give a hint about the requirements for <If


include <if> in the list of things that are directory contexts before
clicking through to the sections.html




git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1544630 13f79535-47bb-0310-9956-ffa450edef68