backport:

- markup & reformatting
- changed overloaded <seealso>s to (hopefully) better ones
- added rather specialized <seealso>s to the directive descriptions
- one may specify more than one language in the content-language header


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/APACHE_2_0_BRANCH@97980 13f79535-47bb-0310-9956-ffa450edef68