Replace highlighter css, in case we replace <example> with <highlight> while...

Replace highlighter css, in case we replace <example> with <highlight> while backporting changes, so they don't stand out as ugly white fields.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@1363376 13f79535-47bb-0310-9956-ffa450edef68