- Add <ElseIf> and <Else> to complement <If> sections. These are both easier

  to use and more efficient than using several <If> sections.
- Update <If> documentation a bit.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1132469 13f79535-47bb-0310-9956-ffa450edef68