Rewritemap improvement:

- map designations are now case insensitive (txt: rNd: PRG: INt:)
- maps may be relative to serverroot, which appears to be _very_
  helpful


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@100860 13f79535-47bb-0310-9956-ffa450edef68