- add several <parentdocument>s

- mention the rewriteguide on misc/index
  (hmm, what about the perf-hp document in /platform/?
   Is it still on topic?)


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@97549 13f79535-47bb-0310-9956-ffa450edef68