Add a note on the overall problem with HEAD requests generating wrong headers.

Again, I believe this is a showstopper, but no one seems to agree with me.

Point at patch for 500/501 problem - I don't plan on testing or committing it.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@95649 13f79535-47bb-0310-9956-ffa450edef68