Add Atom MIME type based on information from:

  http://www.ietf.org/internet-drafts/draft-ietf-atompub-format-00.txt

Also, sync the realaudio mime types from Apache 2.0


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@104301 13f79535-47bb-0310-9956-ffa450edef68